Carbohydrate as a chiral template: optical resolution of N-tert-butanesulfinamides

In this paper, a new efficient strategy for enantioselective synthesis of N-tert-butanesulfinamides with very goods yields and excellent enantiomeric excess via the hydrolysis reaction of N-glycosidic bonds that were formed from D-ribose, under basic conditions was described.
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Carbohydrate as a chiral template: optical resolution of N-tert-butanesulfinamidesVietnam Journal of Chemistry, International Edition, 55(2): 231-235, 2017DOI: 10.15625/2525-2321.2017-00450Carbohydrate as a chiral template: optical resolution ofN-tert-butanesulfinamidesBui Thuy Trang1, Cao Hai Thuong2*, Chu Chien Huu11Millitary Intistute of Chemistry and Material, Hanoi, Vietnam2Department of Physics and Chemical Engineering, Le Quy Don Technical University, Hanoi, VietnamReceived 15 August 2016; Accepted for publication 11 April 2017AbstractN-tert-butanesulfinamides, a class of amines bearing a sulfinyl group attached to nitrogen, exhibit pyramidalbonding where the non-bonded electron pair located at the sulfur atom acts as a fourth ligand. These compounds areconfigurationally sufficiently stable to be separated into R- and S- enantiomers. Enantiopure N-tert-butanesulfinamidesare important auxiliaries in asymmetric synthesis, and some of them also have useful biological properties. In thispaper, a new efficient strategy for enantioselective synthesis of N-tert-butanesulfinamides with very goods yields andexcellent enantiomeric excess via the hydrolysis reaction of N-glycosidic bonds that were formed from D-ribose, underbasic conditions was described.Keywords. N-tert-butanesulfinamide, N-glycoside, D-ribose, enantiomer, asymmetric synthesis.1. INTRODUCTIONThe past two decades have seen an explosion ininterest in the synthesis and utility of moleculescontaining a stereogenic sulfur center [1]. Sulfoxidesare found in a variety of natural products. They havealso been employed as chiral auxiliaries in a range ofreaction classes, and more recently as chiral ligands.Especially, chiral N-tert-butanesulfinamides areincreasingly being utilized as versitale chiralnitrogen intermediates for the preparation of amines,aminoacids [2]. These amides are useful synthonsfor asymmetric synthesis of biogically activemolecules [3]. Moreover, tert-butanesulfinamide isincreasingly being applied across many additionalresearch areas, including the development ofagrochemicals, natural product synthesis, and thepreparation of chemical tools for a wide range ofbiological investigations. N-tert-butanesulfinamidesexists in two forms as an enantiostereomericmixture: (R)-1 and (S)-1 (figure 1).Figure 1: Two enantiopures of N-tertbutanesulfinamidesThe synthesis and isolation of enantiomericallypure N-tert-butanesulfinamide (1) was first reportedby Ellman and coworkers in 1997 [4]. Since then,several different approaches to the synthesis of thiscompound have been reported, includingenantioselective oxidation [5], resolution of racemicmaterial [6], diastereoselective synthesis utilizingstoichiometric chiral auxiliaries [7], and catalyticenantioselective sulfinyl transfer [8].In this paper, we described a new efficientstrategy for enantioselective synthesis of N-tertbutanesulfinamides with very goods yields andexcellent enantiomeric excess via the hydrolysisreaction of N-glycosidic bonds that were formedfrom D-ribose, under basic conditions.2. EXPERIMENTALAll reagents were obtained commercially andused without further purification. All reactions havebeen carried out under a nitrogen atmosphere anddry conditions. The solvents used were freshlydistilled under anhydrous conditions, unlessotherwise specified. The reaction mixtures havebeen magnetically stirred with Teflon stirring bars,and the temperatures were measured externally. Thereactions have been monitored by thin layerchromatography (TLC) with detection by UV light,or a p-anisaldehyde staining solution. Acros silicagel (60, particle size 0.040-0.063 mm) was used forcolumnchromatography.Nuclearmagnetic231VJC, 55(2), 2017Cao Hai Thuong et al.resonance (NMR) spectra have been recorded withBruker Avance 500 spectrometers. The opticalrotation values have been measured with a PerkinElmer 141 Polarimeter, at 589 nm. Theconcentration was reported in gram per milliliter (c,g. ml-1).Racemic sulfinamides (±)-1 m-CPBA (mChloroperoxybenzoic acid) (7 g, 31 mmol) inCH2Cl2 (50 mL) was added dropwise to a stirredsolution of tert-butanedisulfide (5 g, 28 mmol) inCH2Cl2 (15 mL) at 0 °C over 15 min. The solutionwas stirred for 30 min at 0 °C, thenat roomtemperature until the reaction was complete by TLC(3 h). The reaction mixture was poured into aseparatory funnel containing CH2Cl2 (50 mL) andsaturrated NaHCO3 (50 mL) and further extractedwith CH2Cl2 (2×50 mL). The organic layer wasremoved and washed with saturated NaHCO3 (3×50mL), saturated NaCl (50 mL), dried over Na2SO4and concentrated in vacuo to give 5.17 g (95 %) oftert-butylthiosulfinate: 1H NMR (300 MHz) δ 1.32(sulfide) 1.39 (s, 9H, (CH3)3S), 1.57 (s, 9H,(CH3)3S=O). This intermediate was dissolved inCH2Cl2 (15 mL) and a solution of SO2Cl2 (3.6 g, 27mmol) in CH2Cl2 (5 mL) was added dropwise at0°C. The resulting yellow solution was stirred for 1h allowing it to gradually reach room temperature.Excess SO2Cl2 was removed under vacuum and theresulting product, tert-butylsufinyl chloride, wasdiluted in CH2Cl2 (50 mL) and added dropwise toNH4OH (100 mL) at 0 °C over 30 min. After stirringfor 30 min at room temperature, the reaction mixturewas saturated with NaCl and extracted with CH2Cl2(3x50 mL). The combined organic layers werewashed with saturated NaCl (100 mL), dried overNa2SO4 and concentrated in vacuo to give the crudesulfinamide.Purificationusingflashchromatography (4:1 n-pentane/EtOAc) gave thetitle compound (±)-1 (0.71 g, 22 %) as a white solid:mp 98-100 °C 1H NMR (500 MHz, CDCl3) δ (ppm):2.01 (s, br, 2H (NH2)); 1.32 (s, 9H C(CH3)3). 13CNMR (125MHz, CDCl3) δ (ppm): 26.6; 62.9.2,3-O-Isopropylidene-D-ribose, (2) To a stirredsuspension of D-ribose (40 g, 266 mmol) in acetone(500 mL) was added dropwise concentrated H2SO4(1.5 mL) at room temperature and the react ...