Asymmetric allylboration of 2-N, 3-O-isopropylidene-N-boc-L-serinal: diastereoselective synthesis of the calicheamicin gamma(sub 1)(super I) amino sugar

Asymmetric allylboration of isopropylidene-N-Boc-L-serinal with two different allylboronates modified by tartrate esters results in the formation of an amino sugar of Calicheamicin gamma(sub 1)(super I) and its erythro diasteromer, respectively. A high degree of purity of the starting material ensures good diastereoselectivity of this reaction. The nature of the solvent used determines the conformations of the intermediate methyl pyranosides.