Preparation of N‐Glycosylhydroxylamines and Their Oxidation to Nitrones for the Enantioselective Synthesis of Isoxazolidines

Abstract

N‐benzyl‐ and N‐methyl‐N‐glycosylhydroxylamines 3a−i were conveniently obtained by reaction of sugars with N‐substituted hydroxylamines according to a novel procedure. Subsequent oxidation occurred at the alkyl group, selectively affording the corresponding C‐phenyl‐ and C‐unsubstituted N‐glycosylnitrones. C‐phenyl‐N‐glycosylnitrones 10 and 13 underwent highly stereoselective 1,3‐dipolar cycloaddition with dimethyl maleate, with the sugar moiety acting as a chiral auxiliary. Final removal of the glycosyl moiety afforded enantiopure enantiomeric isoxazolidines 17 and ent‐17 which are oxa‐analogues of proline diester derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Glycoside Mimics from Glycosylamines: Recent Progress

“…Alternatively, they were prepared by stirring a suspension of N -benzylhydroxylamine hydrochloride, 3 Å molecular sieves and the hemiacetal derivatives in dry pyridine at room temperature [80]. …”

“…Although the equilibrium is largely or completely shifted to cyclic hydroxylamines, these forms undergo reactions with various lithium and magnesium reagents at low temperature to give the corresponding adducts ( 47 ), albeit often in inseparable mixtures of diastereomers ( route a , Scheme 16) [77,78,80,81]. …”

Product Class 5: Hydroxylamines

“…[267] Scheme 66 Synthesis of Polyfunctional N,N-Dialkylhydroxylamines from Allyl Esters [267] Variation 9: From N-Substituted Hydroxylamines and Sugar Derivatives N-Alkylhydroxylamines react with sugar derivatives to give N-alkyl-N-glycosylhydroxylamines, useful reagents for stereoselective synthesis. [268][269][270][271] For example, reaction of N-benzylhydroxylamine with 2,3,4,6-tetra-O-benzyl-D-glucopyranose (201) in absolute pyridine produces N-benzyl-2,3,4,6-tetra-O-benzyl-N-hydroxy-b-D-glucopyranosylamine (202) in 79% yield (Scheme 68). [270] The glycosylated hydroxylamines listed in Table 2 are prepared analogously.…”

“…[268][269][270][271] For example, reaction of N-benzylhydroxylamine with 2,3,4,6-tetra-O-benzyl-D-glucopyranose (201) in absolute pyridine produces N-benzyl-2,3,4,6-tetra-O-benzyl-N-hydroxy-b-D-glucopyranosylamine (202) in 79% yield (Scheme 68). [270] The glycosylated hydroxylamines listed in Table 2 are prepared analogously. [270,271] Scheme 68 Synthesis of N-Benzyl-2,3,4,6-tetra-O-benzyl-N-hydroxy-b-Dglucopyranosylamine [270] O BnO …”

Diastereoselective Synthesis and Antifungal Activity of Glycosyl Isoxazolines

“…Reagents & condition: (i) NH 2 OH, DMAP, Alcohol, Pyridine, rt (ii) NCS, CH 3 CN, rt (iii) DBU, 08 to rt.…”