SYNTHESIS OF VALIOLAMINE AND ITS N-SUBSTITUTED DERIVATIVES AO-128, VALIDOXYLAMINE-G, AND VALIDAMYCIN-G VIA BRANCHED-CHAIN INOSOSE DERIVATIVES

Novel synthetic routes to valiolamine (1a) and N-substituted valiolamine derivatives via branched-chain inosose derivatives are described. (1S)-(1(OH),2,4/1,3)-2,3,4-Tri-O-benzyl-1-C-[(benzyloxy)methyl]-5-oxo-1,2,3,4-cyclohexanetetrol (3), a branched-chain inosose derivative prepared from D-glucose, 2 has been converted into 1a via the ketoxime 7 followed by hydrogenation. N-Substituted valiolamine derivatives having strong alpha-D-glucosidase inhibitory activity have been synthesized by the direct reductive amination of the branched-chain inosose derivative 3 with an appropriate amino compound to construct the N-substituent moiety, followed by removal of the O-benzyl protecting group. The stereoselective preparation of two representative derivatives, N-[2-hydroxy-1-(hydroxymethyl)ethyl]valiolamine (2a, AO-128)3 and N-[1R,2R)-2-hydroxyclohexyl]valiolamine (2b)3 is described. Application of branched-chain inosose derivatives 3 and 23 to the total synthesis of natural N-substituted valiolamine derivatives validoxylamine G (5a) and validamycin G (6a) is also described.