T. Sugioka et al., THE CD-EXCITON CHIRALITY METHOD AND BENZOYLATION OF STERICALLY HINDERED ALPHA-GLYCOL BY TRANSESTERIFICATION - FORSKOLIN CASE, Enantiomer, 2(2), 1997, pp. 117-121
The sterically hindered hydroxyl group at the 6-position of 7-deacetyl
forskolin (2) was benzoylated by a trans-esterification reaction of 7
beta-p-bromobenzoate (3), yielding 6 beta-p-bromobenzoate (5), from wh
ich 6 beta,7 beta-bis(p-bromobenzoate) (6) was prepared. The CD spectr
um of 6 showed typical exciton split Cotton effects of positive excito
n chirality establishing the absolute stereochemistry of forskolin (1)
and its family compounds. The additivity rule of CD exciton Cotton ef
fects was confirmed in the case of forskolin derivatives.