Synthetic studies on voglibose

Abstract

We have studied the synthesis of voglibose. For the synthesis of voglibose, in the first trial, we tried installment of diol 52 according to Sharpless asymmetric dihydroxylation. 52 was prepared from 48 and then it reacted with either Wittig reaction using allyl phosphonium salt 51 or Julia olefination using allyl sulfone benzothiazle 54. But both reactions did not yield good result. Due to inefficiency of diol installment strategy, introduction of the inner double bond was delayed after cyclization. 48 was converted to 55 and its protected dienes underwent ring closing metathesis with Grubbs second generation catalyst. But the following elimination reaction did not proceed. In the second trial, we prepared allylic alcohol 88. Iodocyclization of 88 did not proceed at all. Alternatively, we prepared 94 via nucleophilic addition of 92 with azide, though it was the minor product. Finally we tried Sharpless asymmetric aminohydroxylation with 82, 96, and 97. Unfortunately it did not produce the desired product. So the preparation of 1 still remains to be solved.