An efficient stereoselective synthesis of the amino sugar component (E ring) of calicheamicin gamma(I)(1)

A simple, efficient, stereoselective synthesis of the methyl 2,4-dideoxy-4-(ethylamino)-3-O-methyl-beta-L-threo-pentopyranoside 2, corresponding to the E monosaccharide unit (E ring) of calicheamicin 1, is described. The synthetic procedure utilizes the methyl 2-deoxy-beta-D-ribopyranoside 3 as the enantiopure starting material and the acid methanolysis of the intermediate activated aziridine 12 to give the desired amino sugar 2 in 6 steps and in satisfactorily high overall yield (60%). No separation stage is necessary at any point of the synthetic process. (C) 1996 Elsevier Science Ltd