Hiroshi Fukase

Stereoselective conversion of valienamine and validamine into valiolamine

Abstract Methods are described for the stereoselective conversion of valienamine ( 2 ) and validamine ( 3 ) into valiolamine ( 1a ), a new pseudo-amino sugar isolated from the fermentation broth of Streptomyces hygroscopicus subsp. limoneus and which is a stronger α- d -glucosidase inhibitor than 2 and 3 . Treatment of the acyclic carbamates ( 4 ) of 2 with halogenation reagents led to ring closure to afford the halo cyclic carbamates ( 6 ), which were reductively dehalogenated and then hydrolyzed to give 1a . Similar treatment of the exomethylene acyclic carbamate ( 12 ), derived from 3 via 8–11 , resulted in the formation of halo cyclic carbamates ( 14a,b ), which were converted into 1a . The synthesis of epivaliolamine ( 1b ), the C-1 epimer of 1a , starting from 2 and 3 , is also described.

A new method for selective N-acylation of aminoglycoside antibiotics

Abstract Per- N -formylation of aminoglycoside (aminocyclitol) antibiotics followed by mild hydrolysis with aqueous ammonia gave mono- N -deformylated derivatives. Each positional isomer of the mono- N -deformylated derivatives thus obtained was separated by column chromatography on Amberlite CG-50 (NH 4 + ). Acylation of mono- N -deformylated derivatives gave the corresponding mono- N -acylated derivatives. The N -formyl groups of the mono- N -acylates were removed by the treatment with dilute aqueous hydrazine acetate, whereas the newly introduced N -acyl group was stable under these conditions. The 1- N -formyl group of the deoxystreptamine moiety of per- N -formylated aminoglycoside antibiotics containing neamine (or 3′-deoxyneamine) is more readily deformylated than the 3- N -formyl group. In this report, isolation and structural-elucidation studies, including 13 C-n.m.r. spectral assignments, of positional isomers of tri- N -formyl derivatives of xylostasin ( 1 ), 3′-deoxyxylostasin ( 2 ), kanamycin A ( 3 ), and neamine ( 4 ) are described. This selective N -acylation provides a useful method for the preparation of 1- N -modified derivatives, and the synthesis of 3′-deoxybutirosin A ( 2f ) from 2 is described in detail as an example.