Showing papers by "Eric Brown published in 1985"
TL;DR: Methyl α-piperonylhemisuccinate was resolved into both its (R)-(+) and (S)-(−)-antipodes by (−) and (+)-ephedrine, respectively, and in high yields.
21 citations
16 citations
TL;DR: In this article, a chiral reagent was used for the resolution of racemic bases such as α-methylbenzylamine, ephedrine and α-(l-naphthyl)ethylamine.
14 citations
TL;DR: Contrary to the podophyllotoxin series, the glycosylation of (-)-steganol occurred with retention of configuration, and all the synthesized compounds, including distegyl ether, exhibited the starting natural R configuration at C-5.
Abstract: The optically active lignan (-)-steganol was prepared from natural (-)-steganacin by selective deacetylation and was transformed, via a three-step sequence, into the corresponding 4', 6'-O-ethylidene- and thenylidene-beta-D-glucopyranosides, 3b and 3c, respectively, which are the analogues, in the steganol series, of the podophyllotoxin derived, and clinically useful, anticancer drugs, VP16-213 and VM26. Formation of the dimeric compound distegyl ether as a minor by-product was established. Complete elucidation of all the asymmetric centres was performed with the help of high resolution 1H-nmr studies at 400 MHz, COSY experiment at 500 MHz and X-ray analysis. Contrary to the podophyllotoxin series, the glycosylation of (-)-steganol occurred with retention of configuration, and all the synthesized compounds, including distegyl ether, exhibited the starting natural R configuration at C-5.
6 citations