The synthesis of ester and ketone analogues of 1-deoxynojirimycin and castanospermine

1-Amino-1-deoxy-D-glucitol (3) was converted into the 3,4;5,6-di-O-isopropylidene protected ammonium salt 17 which was transformed further into the trans-fused piperidine acetonides 4-8 in six steps and 23-32% overall yield. In the final step, ring closure was effected via cleavage of the N-Boc group of intermediates 27-29 with trimethylsilyl iodide: this enabled internal, face selective 1,4-addition of the free amino group to the (5,6)-α,β-unsaturated carbonyl moiety. Further modification and (or) deprotection of compounds 4-8 afforded the piperidine and indolizidine imino sugars 9-12 and 14-15.