First enantioselective synthesis of isagarin, a natural product isolated from Pentas longiflora Oliv

For the first time, an enantioselective synthesis of both 1 R,4 S-isagarin 1a and 1 S,4 R-isagarin 1b was achieved starting from 1,4-dimethoxy-2-vinylnaphthalene 2. The key steps involve a Sharpless asymmetric dihydroxylation and reaction with an acetonylating pyridinium ylid. The different optical rotations and melting points of the enantiopure 1 R,4 S-isagarin 1a and 1 S,4 R-isagarin 1b with respect to the isolated natural product will be addressed. [Display omitted]