Next Article in Journal
Exopolysaccharide from Lactobacillus plantarum HY7714 Protects against Skin Aging through Skin–Gut Axis Communication
Next Article in Special Issue
Synthesis of a New β-Galactosidase Inhibitor Displaying Pharmacological Chaperone Properties for GM1 Gangliosidosis
Previous Article in Journal
Effect of Penetration Enhancers on Toenail Delivery of Efinaconazole from Hydroalcoholic Preparations
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Molecules
Volume 26
Issue 6
10.3390/molecules26061652
molecules-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Synthesis of Piperidine Nucleosides as Conformationally Restricted Immucillin Mimics

by
Maria De Fenza
1,
Anna Esposito
1,
Daniele D’Alonzo
1 and
Annalisa Guaragna
2,*
1
Department of Chemical Sciences, University of Naples Federico II, Via Cintia, 80126 Naples, Italy
2
Department of Chemical, Materials and Production Engineering, University of Naples Federico II, Piazzale V. Tecchio 80, 80125 Naples, Italy
*
Author to whom correspondence should be addressed.
Molecules 2021, 26(6), 1652; https://doi.org/10.3390/molecules26061652
Submission received: 25 February 2021 / Revised: 11 March 2021 / Accepted: 11 March 2021 / Published: 16 March 2021
(This article belongs to the Special Issue Synthesis and Therapeutic Applications of Iminosugars)
Browse Figures
Versions Notes

Abstract

:
The de novo synthesis of piperidine nucleosides from our homologating agent 5,6-dihydro-1,4-dithiin is herein reported. The structure and conformation of nucleosides were conceived to faithfully resemble the well-known nucleoside drugs Immucillins H and A in their bioactive conformation. NMR analysis of the synthesized compounds confirmed that they adopt an iminosugar conformation bearing the nucleobases and the hydroxyl groups in the appropriate orientation.

1. Introduction

The modulation of the activity of carbohydrate processing enzymes represents an important therapeutic target, given the involvement of these proteins in a plethora of metabolic events causing a variety of diverse pathologies [1,2,3]. Over the last decades, intense efforts have been focused on the identification of inhibitors or enhancers of such enzymes [1,4,5,6,7] with promising therapeutic applications for the treatment of viral infections [8,9], cancer [10], diabetes [11], tuberculosis, lysosomal storage diseases [12], and parasitic protozoa [13]. An illustrative example in this area is represented by the class of iminosugars [4,5,7,14], glycomimetics (carbohydrate analogues) having the ring oxygen replaced by an amino group. Iminosugars are able to mimic the transition state of carbohydrate hydrolysis or transfer [15] (involving, in both cases, an upcoming glycosyl oxycarbenium cation), therefore interfering with the activity of carbohydrate-processing enzymes, such as glycosidases and glycosyltransferases [16]. Some among the most important examples of iminosugars include polyhydroxylated piperidines Miglitol, Miglustat, and Migalastat (Figure 1), which are FDA-approved drugs for the treatment of type 2 diabetes [17], Gaucher [18] and Niemann-Pick type C [19], and Fabry disease [20], respectively. Piperidine iminosugars belonging to the unnatural l-series (l-iminosugars) also exhibit pharmacological properties, such as in the case of l-DGJ [21], l-NBDNJ [22] (Figure 1), and its congeners [23,24]. Similarly, iminosugars with a pyrrolidine skeleton (in both enantiomeric series) have been found to hold excellent glycomimetic properties, as in the case of naturally occurring Radicamine A and B [25], 2,5-dideoxy-2,5-imino-d-mannitol (d-DMDP), 1,4-dideoxy-1,4-imino-d-arabinitol (d-DAB-1) (Figure 1), and their structurally related compounds [26,27]. Polyhydroxylated pyrrolidine scaffolds can also be recognized in the structure of Immucillins, which are chemically stable 9-deazapurine C-nucleoside analogues endowed with a variety of therapeutic applications, ranging from the treatment of cancer and autoimmune disorders to parasitic and viral infections [28]. Immucillin-A (1, Imm-A, also known as BCX4430 or Galidesivir, Figure 2) has demonstrated to be active in in vivo models against a variety of RNA-dependent RNA polymerases (RdRp)-based pathogens, including Ebola, Marburg, Yellow Fever, and Zika viruses [29,30].
The molecule has exerted a broad-spectrum activity in vitro against more than 20 RNA viruses belonging to nine different families, such as flaviviruses, filoviruses and also bunyaviruses, togaviruses, paramyxoviruses, coronaviruses, and arenaviruses [31]. Lately, clinical studies have been undertaken to explore the safety and antiviral properties of Galidesivir in patients with COVID-19 [32,33]. On the other side, Immucillin H (2, Imm-H, also known as Forodesine or Mundesine, Figure 2), which is the result of a rational design process and has been at the core of intense kinetic investigations by Schramm et al., is a picomolar inhibitor of bovine and human purine nucleoside phosphorylases [34,35] (PNP, E.C. 2.4.2.1). PNP is a ubiquitous nucleoside processing enzyme essential for DNA and RNA synthesis and it is involved in the reversible phosphorolysis of purine nucleosides to the corresponding bases and (deoxy)ribose-α-1-phosphate. Based on the observation that PNP inhibition stops the growth of activated T-cells, Immucillin-H has been identified as a key candidate for the treatment of leukemia and autoimmune diseases [36].
Over the last decades, further design endeavours have led to the identification of a new generation of Imm-H related PNP inhibitors, endowed with an even higher potency than the parent pyrrolidine nucleoside [37]. All these inhibitors shared an increase of conformational freedom degrees compared with Imm-H [37]. With the aim to provide an alternative strategy to PNP inhibitors, we conceived to replace the pyrrolidine scaffold with a conformationally more restricted biomimetic system. Our approach exploits the well-known finding that the quality of host-guest interactions benefits from the increase in the preorganization of the guest, since no entropy penalty is involved in the binding process. As demonstrative examples, conformationally restricted nucleosides bearing a six-membered sugar unit have already been found to hold an excellent biomimetic potential in various therapeutic contexts [38,39], as a result of the resemblance of natural ribofuranosyl nucleosides in their bioactive conformations [40]. Accordingly, following our longstanding interest in the identification of conformationally restricted molecules with biomimetic properties [39,41,42,43,44,45,46], we undertook the synthesis of novel Immucillin-A and Immucillin-H analogues, i.e., polyhydroxylated piperidine nucleosides 3 and 4 (Figure 2). Our goal was to replace the five membered pyrrolidine scaffold of the drug candidates with a biomimetic six-membered unit. Indeed, among the two chair conformations that 3 and 4 are expected to be able to adopt, the 1C4 form mimics the bioactive 3E conformation of Immucillins when bound to the PNP active site [37]. On this basis, this preliminary study is first aimed to tune up the synthetic path using natural nucleobases as model aglycones, in view of the synthesis of the congeners equipped with the more complex 9-deazapurine nucleobases. Indeed, differently from pyrrolidine nucleosides, move of the nucleobase from C1’ to C2’ in piperidine nucleosides, required for Immucillin biomimicry, allows to install natural nucleobases without affecting the structural integrity of the molecule. In addition, the analysis of the conformational preferences of 3 and 4 is herein performed to ascertain the biomimetic properties of this novel class of nucleoside analogues.

2. Results and Discussion

The synthesis of nucleosides 3 and 4 was achieved from heterocyclic system 7, in turn obtained in a few steps by dithiin 5 and (R)-Garner aldehyde (6) (Scheme 1), using a similar synthetic sequence previously enabling the synthesis of unnatural l-iminosugars [22,23,47]. Deacetylation of 7 under Zemplén conditions (NaOMe, MeOH) quantitatively afforded 8 (96%), which was then treated with Raney®-Ni in EtOH to cleave the dithioethylene bridge, yielding olefin 9 (76% yield). Stereoselective 4-OH-directed epoxidation of 9, using mCPBA in CH2Cl2 led, as expected, exclusively to cis oxirane 10 (75% yield). In the subsequent ketalization step of OH groups in 10, we used an alternative procedure to the standard protocol (PTSA, 2,2-dimethoxypropane, 2-methoxypropene) [48], in order to avoid strictly anhydrous conditions, which are typically required to limit by-product formation derived from acid-catalysed oxirane ring opening. Exploiting our longstanding expertise in the field [23,49,50,51,52,53], we chose the procedure involving the use of polymer-supported triphenyl phosphine (PS-TPP)/I2/imidazole (ImH) system as the activating agent for the protection reaction, using acetone as the acetonide source. In this case, the reaction involves the activation of acetone by the triphenylphosphonium iodide and the subsequent double attack by the diol to the activated ketone. Challenging for our synthetic target, PS-TPP/I2/ImH is also reported to enable epoxide ring opening, to provide the corresponding iodohydrins [54].
However, in our hands, the addition of 10 to a suspension of the premixed activating agent in the anhydrous acetone provided, already after 1 h at room temperature, the corresponding 4’,6’-O-isopropylidene derivative 11 with no traces of other byproducts. The pure ketal 11 could be isolated after a simple filtration of the reaction mixture, increasing the synthetic benefits of the procedure.
With the fully protected epoxide 11 in hand, piperidine nucleosides were eventually obtained, as already reported for similar substrates [42]. By virtue of the locked conformation of compound 11, the treatment of the latter with DBU and adenine in anhydrous DMF at 120 °C (Scheme 2) only led to the epoxide ring opening by the nucleobase at the desired C2 axial position, affording regioselectively the corresponding protected altritol-like nucleoside 12, additionally in a very good yield (86%). Under the same coupling conditions, the treatment of 11 with 6-chloropurine provided a mixture of chloropurine and hypoxanthine-containing nucleosides 13 (82%) and 14 (18%), respectively. Alternatively, the same reaction carried out replacing DBU with NaH in DMF at room temperature yielded 6-chloropurine nucleoside as the only observed product. The quantitative conversion of 13 into 14 could be then obtained by the treatment with a refluxing 0.5 M NaOH solution, while the corresponding adenosine derivative 12 could be obtained by the treatment of 13 with conc. NH4OH at reflux temperature. Eventually, the subsequent addition of 2 M HCl to crude nucleosides 12 and 14 allowed both isopropylidene and Boc groups removal, providing the corresponding nucleosides 3 and 4 as HCl salts (3: > 99% from 12; 4: 84% from 13).
The NMR analysis of nucleosides 3 and 4 confirmed the formation of N9-C2’ bonds, as revealed by HMBC correlations between H-2’ of the piperidine and the C-4 of purines. Furthermore, 1D and 2D spectra strongly suggested that the desired conformations with equatorially oriented nucleobases were adopted by both nucleosides (Figure 3). Indeed, 1H NMR analysis provided large coupling constants between H-1’/H-2’ (10.8 Hz in both cases) and H-2’/H-3’ (3: 10.2 Hz; 4: 10.0 Hz), as well as relatively small coupling constants between H-4’/H-5’ (3: 3.1 Hz; 4: 3.4 Hz), which are responsible for the trans diequatorial interaction between the two protons. On the other hand, the NOESY analysis revealed dipolar interactions between the axially oriented H-1’ and H-6’a (Figure 3).
The observed piperidine conformation is opposite to the 4C1 form (axially oriented nucleobase) adopted by altro-configured nucleosides having a ring oxygen and more generally by the majority of biomimetic hexitol nucleosides [40,55]. Conversely, the conformation of 3 and 4 is in line with those adopted by cyclohexanyl nucleosides, having a methylene group in place of ring heteroatom [42,56]. In agreement with previous studies on both hexitol and cyclohexanyl nucleosides [56], it is conceivable to hypothesize that the conformation of piperidine nucleosides is adopted to relieve the 1,3-diaxial strains involving the nucleobase and hydrogen atoms from C4 and the protonated amino group in the 4C1 conformer (Figure 3).
Having equatorially oriented nucleobases, nucleosides 3 and 4 hold the conformational requirements to mimic the 3E pyrrolidine ring puckering of Immucillins H and A. Based on these data, the piperidine core can be therefore considered as an appropriate scaffold for the construction of preorganized Immucillin analogues.

3. Materials and Methods

3.1. Chemistry

All chemicals and solvents were purchased with the highest degree of purity (Sigma-Aldrich, Darmstadt, Germany; Alfa Aesar, Karlsruhe, Germany; VWR, Milan, Italy) and used without further purification. The reactions were monitored by TLC (precoated silica gel plate F254, Merck, Darmstadt, Germany) and the products were detected by exposure to ultraviolet radiation, iodine vapor, and chromic mixture. Column chromatography: Merck Kieselgel 60 (70–230 mesh). The purity of compounds was determined by CHNS analysis and was ≥ 95% in all cases. NMR spectra were acquired on NMR spectrometers operating at 200 MHz (Varian, Palo Alto, California), 400 MHz (Bruker AVANCE, Billerica, Massachusetts, US) or 500 MHz (Varian Inova, Palo Alto, California, US), using CDCl3 solutions unless otherwise specified. Coupling constant values (J) were reported in Hz, details in Supplementary Materials.

3.2. Procedures for the Synthesis of 3–13

Bicyclic Compound 8. MeONa (16 mg, 0.30 mmol) was added to a stirring solution of 7 [47] (0.12 g, 0.30 mmol) in MeOH (2.0 mL). The mixture was stirred for 4 h at room temperature and then neutralized with a few drops of acetic acid. Then, solvent removal under reduced pressure and chromatography of the crude residue over silica gel (hexane/EtOAc = 6/4) provided pure 2 (92 mg, 96% yield) as a colorless oil. [α]25D + 47.2 (c 0.22, MeOH). 1H NMR (200 MHz): 1.48 (s, 9H), 1.68 (bs 2H), 3.19–3.26 (m, 4H), 3.56–3.68 (m, 3H), 3.90 (bs, 1H), 4.19–4.32 (m, 1H), 4.48–4.56 (m, 1H). 13C NMR (50 MHz): 27.8, 28.2, 44.8, 58.3, 60.6, 68.0, 81.0, 119.9, 121.5, 145.9, 155.7 ppm. Anal. calcd for C13H21NS2O4: C 48.88, H 6.63, N 4.38, S 20.07. Found: C 48.98, H 6.61, N 4.39, S 20.02.
Diol 9. To a suspension of Raney-Ni (W2) (0.90 g, wet) in EtOH (1 mL) a solution of bicycle piperidine 8 (90 mg, 0.28 mmol) in the same solvent (3 mL) at 0 °C was added. The suspension was stirred for 2 h at room temperature, then the solid was filtered off and washed with EtOH. The filtrate was concentrated under reduced pressure providing the crude residue whose chromatography over silica gel (hexane/acetone = 6/4) gave pure 9 (49 mg, 76% yield) as a colorless oil. [α]25D + 87.8 (c 0.85, CHCl3). NMR data for 9 were consistent with those reported elsewhere [57]. Anal. calcd for C11H19NO4: C 57.63, H 8.35, N 6.11. Found: C 57.73, H 8.83, N 6.10.
Epoxide 10. To a stirred solution of diol 9 (49 mg, 0.21 mmol) in anhydrous CH2Cl2 (2 mL), m-CPBA (43 mg, 0.25 mmol) was added at 0 °C. The mixture was stirred for 48 h at room temperature and then aq. NaHCO3 was added and the mixture was extracted with CH2Cl2. The organic layer was dried (Na2SO4) and the solvent evaporated under reduced pressure. Chromatography of the crude residue over silica gel (hexane/EtOAc = 1:9) afforded pure 10 (40 mg, 75% yield): oily, [α]25D + 14.3 (c 1.0, CHCl3). 1H NMR (400 MHz): δ 1.46 (s, 9H), 2.20 (bs, D2O exchange, 2H), 3.31 (bs, 1H), 3.39 (bd, J = 3.8, 1H), 3.46 (t, J = 4.5, 1H), 3.59 (d, J = 8.0, 11.3, 1H), 3.68 (dd, J = 6.0, 11.3, 1H), 3.94 (dd, J = 1.4, 4.5, 1H), 4.18 (bt, J = 6.0, 1H), 4.28 (bs, 1H). 13C NMR (100 MHz): 24.3, 47.5, 48.3, 52.9, 56.4, 58.5, 7.2, 76.9, 152.4 ppm. Anal. calcd for C11H19NO5: C 53.87, H 7.81, N 5.71. Found: C 53.96, H 7.79, N 5.72.
Protected Epoxide 11. To a magnetically stirred solution of polymer supported triphenylphosphine (PS-TPP; 100–200 mesh, extent of labeling: ~3 mmol/g triphenylphosphine loading) (80 mg, ~0.24 mmol) in anhydrous acetone (0.5 mL) at room temperature, a solution of I2 (60 mg, 0.24 mmol) in the same solvent (0.7 mL) was added dropwise in the dark and under dry N2 atmosphere. Subsequently imidazole (32 mg, 0.48 mmol) was added and after 15 min 10 (40 mg, 0.16 mmol) was added in one portion to the suspension. TLC monitoring showed the complete consumption of starting sugar within 10 min. The resulting mixture was filtered and the solvent removed at room temperature under reduced pressure, affording 11 (36 mg, 79% yield) as a colorless oil. [α]25D + 1.2 (c 2.0, CHCl3). 1H NMR (500 MHz, acetone-d6): δ 1.35 (s, 3H), 1.46 (s, 9H), 1.52 (s, 3H), 3.26 (d, J = 4.8, 1H), 3.31 (td, J = 4.8, 10.7 1H), 3.41–3.44 (m, 1H), 3.76 (d, J = 15.3, 1H), 3.83 (dd, J = 2.0, 15.3, 1H), 4.15 (t, J = 10.7, 1H), 4.23 (dd, J = 4.8, 10.7, 1H), 4.37 (d, J = 10.7, 1H). 13C NMR (125 MHz, acetone-d6): 18.6, 27.5, 29.7, 42.6, 51.0, 51.8, 62.4, 69.5, 79.8, 98.9, 154.4 ppm. Anal. calcd for C14H23NO5: C 58.93, H 8.13, N 4.91. Found: C 59.06, H 8.1, N 4.92.
Nucleoside 12. Adenine (36 mg, 0.26 mmol) and epoxide 11 (35 mg, 0.12 mmol) were suspended in anhydrous DMF (0.9 mL) for 15 min, at room temperature under Ar atmosphere. Then, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, 0.26 mmol, 39 uL) was added and the resulting mixture was heated at 90 °C and stirred for 72 h. The reaction mixture was cooled to room temperature, quenched with sat.aq. NH4Cl, and concentrated under reduced pressure. The crude residue was extracted with EtOAc and washed with brine. The organic layers were dried (Na2SO4) and the solvent evaporated under reduced pressure. Chromatography of the crude residue over silica gel (EtOAc:MeOH = 9:1) gave pure 12 (43 mg, 86% yield): oily, [α]25D − 21.2 (c 1.0, MeOH). 1H NMR (400 MHz, CD3OD): δ 1.44 (s, 3H), 1.47 (s, 9H), 1.60 (s, 3H), 3.78 (td, J = 4.7, 10.5, 1H), 3.98 (dd, J = 5.2, 13.9, 1H), 4.03–4.12 (m, 2H), 4.34 (bt, J = 2.7, 1H), 4.38 (dd, J = 4.7, 10.5 Hz, 1H), 4.60–4.65 (m, 2H), 8.21 (s, 1H), 8.22 (s, 1H).13C NMR (100 MHz, CD3OD): 19.6, 28.5, 29.4, 42.9, 59.8, 63.9, 70.2, 70.9, 82.4, 100.7, 120.2, 141.5, 150.8, 153.8, 156.6, 157.5 ppm. Anal. calcd for C19H28N6O5: C 54.27, H 6.71, N 19.99. Found: C 54.27, H 6.73, N 20.05.
Nucleoside 13. 6-Chloropurine (31 mg, 0.20 mmol) and epoxide 11 (25 mg, 0.09 mmol) were suspended in anhydrous DMF (0.5 mL) at room temperature under Ar atmosphere. After 15 min, 1,8-diazobicyclo[5.4.0]undec-7-ene (DBU, 30 μL, 0.20 mmol) was added and the reaction mixture was heated at 120 °C and stirred for 72 h. Then, the reaction mixture was cooled to room temperature, quenched with NH4Cl, and concentrated under reduced pressure. The crude residue was extracted with DCM and washed with brine. The organic layers were dried (Na2SO4) and the solvent evaporated under reduced pressure. Flash chromatography of the crude residue over silica gel (AcOEt) gave pure 13 (32 mg, 82% yield): oily, [α]25D + 3.3 (c 0.33, acetone). 1H NMR (CDCl3, 500 MHz): δ 1.42 (s, 3H), 1.45 (s, 9H), 1.50 (s, 3H), 3.54 (bs, 1H), 3.67 (td, J = 10.5, 4.9 Hz, 1H), 3.89 (dd, J = 14.3, 4.4 Hz, 1H), 4.12 (t, J = 11.0 Hz, 1H), 4.17 (dd, J = 3.0, 10.5 Hz, 1H), 4.27 (dd, J = 14.3, 6.0 Hz, 1H), 4.36 (t, J = 2.9 Hz, 1H), 4.51 (dd, J = 11.5, 4.9 Hz, 1H), 4.62–4.64 (m, 1H), 7.87 (s, 1H), 8.32 (s, 1H). 13C NMR (100 MHz): 19.6, 28.5, 29.3, 42.8, 49.6, 55.9, 63.0, 68.6, 69.7, 81.7, 99.4, 120.3, 137.0, 150.6, 152.6, 154.7 ppm. Anal. calcd for C19H26ClN5O5: C 51.88, H 5.96, Cl 8.06, N 15.92. Found: C 51.77, H 5.94, Cl 8.09, N 15.97.
Adenosine analogue 3. Procedure A (from 12). 2 M HCl (11.6 mL) was added to a solution of 12 (40 mg, 0.09 mmol) in THF (0.6 mL) and the reaction mixture was heated to reflux temperature for 1 h. Removal of the volatiles under reduced pressure and subsequent trituration with Et2O afforded 3 as hydrochloride salt (30 mg, quant.). Procedure B (from 13). Compound 13 (15 mg, 0.03 mmol) was treated with 13 m NH4OH (4.5 mL). The mixture was added to a steal bomb reactor heated to reflux temperature for 72 h. The reaction was quenched by the addition of a few drops of HCl (1n) and concentrated under reduced pressure. The crude residue was then diluted with CHCl3 : MeOH = 8:2 and filtered under a silica pad. Volatiles were removed under reduced pressure to obtain 12 a white solid. As described in procedure A, THF (2 mL) and HCl 2 m (0.6 mL) were then added and the solution was heated to reflux temperature for 1 h. Removal of the solvents under reduced pressure and the subsequent trituration of the solid with Et2O gave pure 3 as hydrochloride salt (7.0 mg, 65% yield over two steps). Data for 3: white solid, [α]25D −8.25 (c 0.14, H2O). 1H NMR (400 MHz, D2O): δ 3.76 (dd, J = 5.2, 13.4, 1H), 3.90 (dt, J = 3.5, 8.8, 1H), 4.03 (dd, J = 10.5, 13.4, 1H), 4.07 (dd, J = 3.5, 12.8, 1H), 4.16 (dd, J = 8.8, 12.8, 1H), 4.31 (t, J = 3.5 Hz, 1H), 4.62 (dd, J = 3.5, 10.5, 1H), 5.19 (td, J = 5.2, 10.5, 1H), 8.38 (s, 1H), 8.39 (s, 1H). 13C NMR (100 MHz, D2O): 39.7, 53.3, 55.8, 59.9, 65.9, 66.9, 118.9, 144.2, 144.4, 148.6, 149.9 ppm. Anal. calcd for C11H17ClN6O3: C 41.71, H 5.41, Cl 11.19, N 26.53. Found: C 41.56, H 5.39, Cl 11.24, N 26.63.
Hypoxanthine analogue 4. Nucleoside 13 (15 mg, 0.03 mmol) was refluxed for 2 h in a 0.5 n aq NaOH (0.5 mL). Then, the reaction mixture was cooled to 0 °C and 0.5 n HCl was carefully added (0.8 mL). The solution was evaporated under reduced pressure. The crude was then dissolved in THF (0.2 mL) and then 2 m HCl (0.5 mL) was added. The reaction mixture was heated to reflux temperature for 3 h. Then, the solvent was evaporated under reduced pressure and the subsequent trituration of the solid with Et2O gave pure 4 as hydrochloride salt (8.0 mg, 84%). [α]25D + 2.8 (c 0.14, H2O). 1H NMR (400 MHz, D2O): δ 3.74 (dd, J = 5.1, 13.3, 1H), 3.89 (m, 1H), 4.02 (dd, J = 10.8, 13.3, 1H), 4.05 (dd, J = 3.4, 12.8, 1H), 4.15 (dd, J = 8.9, 12.8, 1H), 4.30 (t, J = 3.4 Hz, 1H), 4.61 (dd, J = 3.3, 10.0, 1H), 5.18 (td, J = 5.1, 10.0, 1H), 8.40 (s, 1H), 8.42 (s, 1H). 13C NMR (100 MHz, D2O): 35.8, 49.1, 51.8, 55.9, 62.0, 62.8, 115.6, 123.4, 138.6, 140.5, 144.3 ppm. Anal. calcd for C11H16ClN5O4: C 41.58, H 5.08, Cl 11.16, N 22.04. Found: C 41.49, H 5.10, Cl 11.18, N 22.04.

4. Conclusions

The synthesis of piperidine nucleosides 3 and 4, acting as conformationally restricted analogues of Immucillins H and A, has been herein reported. Our approach exploits our consolidated strategy, involving the synthetic manipulation of coupling product 7 starting from our three-carbon homologating agent 5. The stereoselective preparation of cis epoxide 11 and the subsequent coupling reaction in two alternative approaches with model nucleobases have enabled access to piperidine nucleosides 3 and 4 with the desired d-altro configuration. NMR analysis demonstrated that both compounds resemble the bioactive conformation of Immucillins H and A, as they adopt iminosugar conformations with equatorially oriented nucleobases. Further studies will be devoted to explore the suitability of our approach to introduce a variety of other heterocyclic bases for SAR analysis. Particularly, synthetic studies aimed to incorporate Immucillin-mimicking 9-deazapurine nucleobases and in vitro assays, aimed to ascertain the pharmacological potential of all the synthesised nucleosides, are currently ongoing and will be published elsewhere.

Supplementary Materials

Figure S1: 1H and 13C NMR spectra of compound 8; Figure S2: 1H and 13C NMR spectra of compound 10; Figure S3: 1H and 13C spectra of compound 11; Figure S4: 1H and 13C NMR spectra of compound 12; Figure S5: 1H and 13C NMR spectra of compound 13; Figure S6: 1H and 13C NMR spectra of compound 3; Figure S7: 1H and 13C NMR spectra of compound 4.

Author Contributions

Conceptualization, A.G. and D.D.; methodology, A.E.; software, A.E.; validation, M.D.F. and D.D.; formal analysis, M.D.F.; investigation, M.D.F.; data curation, A.E.; writing—original draft preparation, A.G.; writing—review and editing, D.D., M.D.F. and A.E.; supervision, D.D.; project administration, A.G.; funding acquisition, A.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available within the article and in the Supplementary Materials section.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Varki, A.; Cummings, R.D.; Esko, J.D.; Stanley, P.; Hart, G.W.; Aebi, M.; Darvill, A.G.; Kinoshita, T.; Packer, N.H.; Prestegard, J.H.; et al. Essentials of Glycobiology, 3rd ed.; Cold Spring Harbor Laboratory Press: Cold Spring Harbor, NY, USA, 2009. [Google Scholar]
  2. Gloster, T.M.; Vocadlo, D.J. Developing inhibitors of glycan processing enzymes as tools for enabling glycobiology. Nat. Chem. Biol. 2012, 8, 683–694. [Google Scholar] [CrossRef] [PubMed]
  3. Stütz, A.E.; Wrodnigg, T.M. Carbohydrate-processing enzymes of the lysosome: Diseases caused by misfolded mutants and sugar mimetics as correcting pharmacological chaperones. Adv. Carbohydr. Chem. Biochem. 2016, 73, 225–302. [Google Scholar] [PubMed]
  4. Compain, P.; Martin, O.R. Iminosugars: From Synthesis to Therapeutic Applications, 1st ed.; John Wiley & Sons, Ltd: Chichester, UK, 2007. [Google Scholar]
  5. Horne, G.; Wilson, F.X.; Tinsley, J.; Williams, D.H.; Storer, R. Iminosugars past, present and future: Medicines for tomorrow. Drug Discov. Today 2011, 16, 107–118. [Google Scholar] [CrossRef]
  6. Chao, L.; Jongkees, S. High-Throughput approaches in carbohydrate-active enzymology: Glycosidase and glycosyl transferase inhibitors, evolution, and discovery. Angew. Chem. Int. Ed. 2019, 58, 12750–12760. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  7. Nash, R.J.; Kato, A.; Yu, C.-Y.; Fleet, G.W. Iminosugars as therapeutic agents: Recent advances and promising trends. Future Med. Chem. 2011, 3, 1513–1521. [Google Scholar] [CrossRef]
  8. Alonzi, D.S.; Scott, K.A.; Dwek, R.A.; Zitzmann, N. Iminosugar antivirals: The therapeutic sweet spot. Biochem. Soc. Trans. 2017, 45, 571–582. [Google Scholar] [CrossRef] [Green Version]
  9. Evans DeWald, L.; Starr, C.; Butters, T.; Treston, A.; Warfield, K.L. Iminosugars: A host-targeted approach to combat Flaviviridae infections. Antiviral Res. 2020, 184, 104881. [Google Scholar] [CrossRef] [PubMed]
  10. Wrodnigg, T.; Steiner, A.; Ueberbacher, B. Natural and synthetic iminosugars as carbohydrate processing enzyme inhibitors for cancer therapy. Anticancer. Agents Med. Chem. 2008, 8, 77–85. [Google Scholar] [CrossRef] [PubMed]
  11. Derosa, G.; Maffioli, P. Mini-special issue paper management of diabetic patients with hypoglycemic agents α-glucosidase inhibitors and their use in clinical practice. Arch. Med. Sci. 2012, 5, 899–906. [Google Scholar] [CrossRef]
  12. Platt, F.M.; D’Azzo, A.; Davidson, B.L.; Neufeld, E.F.; Tifft, C.J. Lysosomal storage diseases. Nat. Rev. Dis. Prim. 2018, 4, 27. [Google Scholar] [CrossRef]
  13. Cheviet, T.; Lefebvre-Tournier, I.; Wein, S.; Peyrottes, S. Plasmodium purine metabolism and its inhibition by nucleoside and nucleotide analogues. J. Med. Chem. 2019, 62, 8365–8391. [Google Scholar] [CrossRef] [Green Version]
  14. D’Alonzo, D.; Guaragna, A.; Palumbo, G. Glycomimetics at the mirror: Medicinal chemistry of l-iminosugars. Curr. Med. Chem. 2009, 16, 473–505. [Google Scholar] [CrossRef]
  15. Gloster, T.M.; Davies, G.J. Glycosidase inhibition: Assessing mimicry of the transition state. Org. Biomol. Chem. 2010, 8, 305–320. [Google Scholar] [CrossRef] [Green Version]
  16. Stütz, A.E.; Paulsen, H. Iminosugars as Glycosidase Inhibitors; Wiley-VCH Verlag GmbH: Hoboken, NJ, USA, 1998. [Google Scholar]
  17. Kumar Thakur, A.; Kumar, Y.; K Goyal, K. Pharmacotherapeutics of miglitol: An α-glucosidase inhibitor. J. Anal. Pharm. Res. 2018, 7, 617–619. [Google Scholar] [CrossRef]
  18. Hollak, C.E.M.; Hughes, D.; van Schaik, I.N.; Schwierin, B.; Bembi, B. Miglustat (Zavesca®) in type 1 Gaucher disease: 5-year results of a post-authorisation safety surveillance programme. Pharmacoepidemiol. Drug Saf. 2009, 18, 770–777. [Google Scholar] [CrossRef]
  19. Patterson, M.C.; Mengel, E.; Vanier, M.T.; Moneuse, P.; Rosenberg, D.; Pineda, M. Treatment outcomes following continuous miglustat therapy in patients with Niemann-Pick disease Type C: A final report of the NPC Registry. Orphanet J. Rare Dis. 2020, 15, 104. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  20. Riccio, E.; Zanfardino, M.; Ferreri, L.; Santoro, C.; Cocozza, S.; Capuano, I.; Imbriaco, M.; Feriozzi, S.; Pisani, A. Switch from enzyme replacement therapy to oral chaperone migalastat for treating Fabry disease: Real-life data. Eur. J. Hum. Genet. 2020, 28, 1662–1668. [Google Scholar] [CrossRef] [PubMed]
  21. Jenkinson, S.F.; Fleet, G.W.J.; Nash, R.J.; Koike, Y.; Adachi, I.; Yoshihara, A.; Morimoto, K.; Izumori, K.; Kato, A. Looking-glass synergistic pharmacological chaperones: DGJ and L-DGJ from the enantiomers of tagatose. Org. Lett. 2011, 13, 4064–4067. [Google Scholar] [CrossRef] [PubMed]
  22. D’Alonzo, D.; De Fenza, M.; Porto, C.; Iacono, R.; Huebecker, M.; Cobucci-Ponzano, B.; Priestman, D.A.; Platt, F.; Parenti, G.; Moracci, M.; et al. N-Butyl-l-deoxynojirimycin (l-NBDNJ): Synthesis of an allosteric enhancer of α-glucosidase activity for the treatment of Pompe disease. J. Med. Chem. 2017, 60. [Google Scholar] [CrossRef] [PubMed]
  23. De Fenza, M.; D’Alonzo, D.; Esposito, A.; Munari, S.; Loberto, N.; Santangelo, A.; Lampronti, I.; Tamanini, A.; Rossi, A.; Ranucci, S.; et al. Exploring the effect of chirality on the therapeutic potential of N-alkyl-deoxyiminosugars: Anti-inflammatory response to Pseudomonas aeruginosa infections for application in CF lung disease. Eur. J. Med. Chem. 2019, 175, 63–71. [Google Scholar] [CrossRef] [PubMed]
  24. Esposito, A.; D’Alonzo, D.; De Fenza, M.; De Gregorio, E.; Tamanini, A.; Lippi, G.; Dechecchi, M.C.; Guaragna, A. Synthesis and therapeutic applications of iminosugars in cystic fibrosis. Int. J. Mol. Sci. 2020, 21, 3353. [Google Scholar] [CrossRef] [PubMed]
  25. Shibano, M.; Tsukamoto, D.; Masuda, A.; Tanka, Y.; Kusano, G. Two new pyrrolidine alkaloids, radicamines A and B, as inhibitors of alpha-glucosidase from lobelia chinensis lour. Chem. Pharm. Bull. 2001, 49, 1362–1365. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  26. Haarr, M.B.; Lopéz, Ó.; Pejov, L.; Fernández-Bolaños, J.G.; Lindbäck, E.; Sydnes, M.O. 1,4-Dideoxy-1,4-imino-d-arabinitol (DAB) analogues possessing a hydrazide imide moiety as potent and selective α-mannosidase inhibitors. ACS Omega 2020, 5, 18507–18514. [Google Scholar] [CrossRef] [PubMed]
  27. Asano, N.; Oseki, K.; Kizu, H.; Matsui, K. Nitrogen-in-the-ring pyranoses and furanoses: Structural basis of inhibition of mammalian glycosidases. J. Med. Chem. 1994, 37, 3701–3706. [Google Scholar] [CrossRef]
  28. Evans, G.; Schramm, V.; Tyler, P. The immucillins: Design, synthesis and application of transition- state analogues. Curr. Med. Chem. 2015, 22. [Google Scholar] [CrossRef]
  29. Evans, G.B.; Tyler, P.C.; Schramm, V.L. Immucillins in infectious diseases. ACS Infect. Dis. 2018, 4, 107–117. [Google Scholar] [CrossRef]
  30. Lim, S.-Y.; Osuna, C.E.; Best, K.; Taylor, R.; Chen, E.; Yoon, G.; Kublin, J.L.; Schalk, D.; Schultz-Darken, N.; Capuano, S.; et al. A direct-acting antiviral drug abrogates viremia in Zika virus-infected rhesus macaques. Sci. Transl. Med. 2020, 12, eaau9135. [Google Scholar] [CrossRef]
  31. Warren, T.K.; Wells, J.; Panchal, R.G.; Stuthman, K.S.; Garza, N.L.; Van Tongeren, S.A.; Dong, L.; Retterer, C.J.; Eaton, B.P.; Pegoraro, G.; et al. Protection against filovirus diseases by a novel broad-spectrum nucleoside analogue BCX4430. Nature 2014, 508, 402–405. [Google Scholar] [CrossRef] [Green Version]
  32. Elfiky, A.A. Ribavirin, Remdesivir, Sofosbuvir, Galidesivir, and Tenofovir against SARS-CoV-2 RNA dependent RNA polymerase (RdRp): A molecular docking study. Life Sci. 2020, 253, 117592. [Google Scholar] [CrossRef]
  33. A Study to Evaluate the Safety, Pharmacokinetics and Antiviral Effects of Galidesivir in Yellow Fever or COVID-19; last update: July 23, 2020. Start Date: April 2020. Available online: https://clinicaltrials.gov/ct2/show/NCT03891420 (accessed on 17 November 2020).
  34. Kicska, G.A.; Long, L.; Horig, H.; Fairchild, C.; Tyler, P.C.; Furneaux, R.H.; Schramm, V.L.; Kaufman, H.L. Immucillin H, a powerful transition-state analog inhibitor of purine nucleoside phosphorylase, selectively inhibits human T lymphocytes. Proc. Natl. Acad. Sci. USA 2001, 98, 4593–4598. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  35. Evans, G.B.; Schramm, V.L.; Tyler, P.C. The transition to magic bullets—transition state analogue drug design. Medchemcomm 2018, 9, 1983–1993. [Google Scholar] [CrossRef]
  36. Gandhi, V.; Kilpatrick, J.M.; Plunkett, W.; Ayres, M.; Harman, L.; Du, M.; Bantia, S.; Davisson, J.; Wierda, W.G.; Faderl, S.; et al. A proof-of-principle pharmacokinetic, pharmacodynamic, and clinical study with purine nucleoside phosphorylase inhibitor immucillin-H (BCX-1777, forodesine). Blood 2005, 106, 4253–4260. [Google Scholar] [CrossRef] [Green Version]
  37. Ho, M.-C.; Shi, W.; Rinaldo-Matthis, A.; Tyler, P.C.; Evans, G.B.; Clinch, K.; Almo, S.C.; Schramm, V.L. Four generations of transition-state analogues for human purine nucleoside phosphorylase. Proc. Natl. Acad. Sci. USA 2010, 107, 4805–4812. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  38. Le, B.T.; Chen, S.; Abramov, M.; Herdewijn, P.; Veedu, R.N. Evaluation of anhydrohexitol nucleic acid, cyclohexenyl nucleic acid and D-altritol nucleic acid-modified 2′-O-methyl RNA mixmer antisense oligonucleotides for exon skipping in vitro. Chem. Commun. 2016, 52, 13467–13470. [Google Scholar] [CrossRef]
  39. De Fenza, M.; Eremeeva, E.; Troisi, R.; Yang, H.; Esposito, A.; Sica, F.; Herdewijn, P.; D’Alonzo, D.; Guaragna, A. Structure—activity relationship study of a potent α-thrombin binding aptamer incorporating hexitol nucleotides. Chem. A Eur. J. 2020, 26, 9589–9597. [Google Scholar] [CrossRef]
  40. Herdewijn, P. Nucleic acids with a six-membered ‘carbohydrate’ mimic in the backbone. Chem. Biodivers. 2010, 7, 1–59. [Google Scholar] [CrossRef] [PubMed]
  41. D’Alonzo, D.; Amato, J.; Schepers, G.; Froeyen, M.; Van Aerschot, A.; Herdewijn, P.; Guaragna, A. Enantiomeric selection properties of β-homoDNA: Enhanced pairing for heterochiral complexes. Angew. Chem. Int. Ed. 2013, 52, 6662–6665. [Google Scholar] [CrossRef]
  42. Paolella, C.; D’Alonzo, D.; Schepers, G.; Van Aerschot, A.; Di Fabio, G.; Palumbo, G.; Herdewijn, P.; Guaragna, A. Oligonucleotides containing a ribo-configured cyclohexanyl nucleoside: Probing the role of sugar conformation in base pairing selectivity. Org. Biomol. Chem. 2015, 13, 10041–10049. [Google Scholar] [CrossRef] [PubMed]
  43. D’Alonzo, D.; Froeyen, M.; Schepers, G.; Di Fabio, G.; Van Aerschot, A.; Herdewijn, P.; Palumbo, G.; Guaragna, A. 1′,5′-Anhydro-l-ribo-hexitol adenine nucleic acids (α-L-HNA-A): Synthesis and chiral selection properties in the mirror image world. J. Org. Chem. 2015, 80, 5014–5022. [Google Scholar] [CrossRef]
  44. Esposito, A.; Giovanni, C.; De Fenza, M.; Talarico, G.; Chino, M.; Palumbo, G.; Guaragna, A.; D’Alonzo, D. A stereoconvergent Tsuji—Trost reaction in the synthesis of cyclohexenyl nucleosides. Chem. -Eur. J. 2020, 26, 2597–2601. [Google Scholar] [CrossRef]
  45. Oliviero, G.; Amato, J.; Borbone, N.; D’Errico, S.; Piccialli, G.; Mayol, L. Synthesis of N-1 and ribose modified inosine analogues on solid support. Tetrahedron Lett. 2007, 48, 397–400. [Google Scholar] [CrossRef]
  46. Oliviero, G.; Amato, J.; Borbone, N.; D’Errico, S.; Piccialli, G.; Bucci, E.; Piccialli, V.; Mayol, L. Synthesis of 4-N-alkyl and ribose-modified AICAR analogues on solid support. Tetrahedron 2008, 64, 6475–6481. [Google Scholar] [CrossRef]
  47. Guaragna, A.; D’Errico, S.; D’Alonzo, D.; Pedatella, S.; Palumbo, G. A general approach to the synthesis of 1-deoxy-l-iminosugars. Org. Lett. 2007, 9, 3473–3476. [Google Scholar] [CrossRef]
  48. Böshagen, H.; Heiker, F.-R.; Matthias Schüller, A. The chemistry of the 1-deoxynojirimycin system. Synthesis of 2-acetamido-1,2-dideoxynojirimycin from 1-deoxynojirimycin. Carbohydr. Res. 1987, 164, 141–148. [Google Scholar] [CrossRef]
  49. Pedatella, S.; Guaragna, A.; D’Alonzo, D.; De Nisco, M.; Palumbo, G. Triphenylphosphine polymer-bound/iodine complex: A suitable reagent for the preparation of O-isopropylidene sugar derivatives. Synthesis 2006, 305–308. [Google Scholar] [CrossRef]
  50. Guaragna, A.; Amoresano, A.; Pinto, V.; Monti, G.; Mastrobuoni, G.; Marino, G. Synthesis and proteomic activity evaluation of a new isotope-coded affinity tagging (ICAT) reagent. Bioconjug. Chem. 2008, 19, 1095–1104. [Google Scholar] [CrossRef]
  51. Esposito, A.; De Gregorio, E.; De Fenza, M.; D’Alonzo, D.; Satawani, A.; Guaragna, A. Expeditious synthesis and preliminary antimicrobial activity of deflazacort and its precursors. RSC Adv. 2019, 9, 21519–21524. [Google Scholar] [CrossRef] [Green Version]
  52. De Gregorio, E.; Esposito, A.; Vollaro, A.; De Fenza, M.; D’Alonzo, D.; Migliaccio, A.; Iula, V.D.; Zarrilli, R.; Guaragna, A. N-Nonyloxypentyl-l-deoxynojirimycin inhibits growth, biofilm formation and virulence factors expression of Staphylococcus aureus. Antibiotics 2020, 9, 362. [Google Scholar] [CrossRef] [PubMed]
  53. Esposito, A.; D’Alonzo, D.; D’Errico, S.; De Gregorio, E.; Guaragna, A. Toward the identification of novel antimicrobial agents: One-pot synthesis of lipophilic conjugates of N-alkyl d- and l-iminosugars. Mar. Drugs 2020, 18, 572. [Google Scholar] [CrossRef]
  54. Moussa, Z.; Judeh, Z.M.A.; Ahmed, S.A. Polymer-supported triphenylphosphine: Application in organic synthesis and organometallic reactions. RSC Adv. 2019, 9, 35217–35272. [Google Scholar] [CrossRef] [Green Version]
  55. D’Alonzo, D.; Guaragna, A.; Palumbo, G. Exploring the role of chirality in nucleic acid recognition. Chem. Biodivers. 2011, 8, 373–413. [Google Scholar] [CrossRef] [PubMed]
  56. Maurinsh, Y.; Rosemeyer, H.; Esnouf, R.; Medvedovici, A.; Wang, J.; Ceulemans, G.; Lescrinier, E.; Hendrix, C.; Busson, R.; Sandra, P.; et al. Synthesis and pairing properties of oligonucleotides containing 3-hydroxy-4-hydroxymethyl-1-cyclohexanyl nucleosides. Chem. Eur. J. 1999, 5, 2139–2150. [Google Scholar] [CrossRef]
  57. Rengasamy, R.H.; Curtis-Long, M.J.; Ryu, H.W.; Oh, K.Y.; Park, K.H. Stereoselective synthesis of l-deoxyaltronojirimycin from l-serine. Bull. Korean Chem. Soc. 2009, 30, 1531–1534. [Google Scholar] [CrossRef] [Green Version]
Molecules 26 01652 g001 550
Figure 1. Pyrrolidine and piperidine iminosugars.
Figure 1. Pyrrolidine and piperidine iminosugars.
Molecules 26 01652 g001
Molecules 26 01652 g002 550
Figure 2. Immucillins A and H (1 and 2) and their conformationally restricted mimics 3 and 4.
Figure 2. Immucillins A and H (1 and 2) and their conformationally restricted mimics 3 and 4.
Molecules 26 01652 g002
Molecules 26 01652 sch001 550
Scheme 1. De novo approach to cis epoxide 11.
Scheme 1. De novo approach to cis epoxide 11.
Molecules 26 01652 sch001
Molecules 26 01652 sch002 550
Scheme 2. Synthesis of Immucillin H and A analogues 3 and 4.
Scheme 2. Synthesis of Immucillin H and A analogues 3 and 4.
Molecules 26 01652 sch002
Molecules 26 01652 g003 550
Figure 3. 1H NMR analysis of 3 HCl.
Figure 3. 1H NMR analysis of 3 HCl.
Molecules 26 01652 g003
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

De Fenza, M.; Esposito, A.; D’Alonzo, D.; Guaragna, A. Synthesis of Piperidine Nucleosides as Conformationally Restricted Immucillin Mimics. Molecules 2021, 26, 1652. https://doi.org/10.3390/molecules26061652

AMA Style

De Fenza M, Esposito A, D’Alonzo D, Guaragna A. Synthesis of Piperidine Nucleosides as Conformationally Restricted Immucillin Mimics. Molecules. 2021; 26(6):1652. https://doi.org/10.3390/molecules26061652

Chicago/Turabian Style

De Fenza, Maria, Anna Esposito, Daniele D’Alonzo, and Annalisa Guaragna. 2021. "Synthesis of Piperidine Nucleosides as Conformationally Restricted Immucillin Mimics" Molecules 26, no. 6: 1652. https://doi.org/10.3390/molecules26061652

APA Style

De Fenza, M., Esposito, A., D’Alonzo, D., & Guaragna, A. (2021). Synthesis of Piperidine Nucleosides as Conformationally Restricted Immucillin Mimics. Molecules, 26(6), 1652. https://doi.org/10.3390/molecules26061652

Article Metrics

Back to TopTop