REGIOSELECTIVE AND STEREOSELECTIVE CONJUGATE ADDITION OF NITROGEN NUCLEOPHILES TO 2-ALKENYL N-METHYLTHIAZOLIUM IODIDES - SYNTHESIS OF D-3-EPI-DAUNOSAMINE AND SOME LINCOSAMINE ANALOGS

A two-carbon homologation-amination technology of aldehydes is described. Key steps involve the Michael-type addition of a nitrogen nucleophile (benzylamine, trimethylsilylazide, potassium phtalimide) to a 2-alkenyl N-methylthiazolium salt obtained by olefination of the aldehyde with the phosphorane (1), and the thiazole-to-formyl deblocking. The addition of benzylaminine to the thiazolium salt derived from the acetonide of D- glyceraldehyde occurs with a good level of syn-diastereoselectivity (ds, 85-90 %) in agreement with a modified Felkin-Anh model. This technology is employed in short synthetic routes to D-3-epi-daunosamine from 4-deoxy D-threose and some lincosamine analogues from α-D-dialdogalactopyranose. © 1990.