330671-07-3Relevant academic research and scientific papers
Efficient and stereoselective β-epoxidation of the 16(17)-double bond of gibberellic acid derivatives with an acylperoxy radical generated by irradiation of α-diketones and oxygen
Seto, Hideharu,Hoshino, Mikio,Fujioka, Shozo,Suenaga, Toshiro,Shimizu, Takeshi,Yoshida, Shigeo
, p. 81 - 86 (2007/10/03)
Irradiation of gibberellic acid derivatives in the presence of α-diketones in an oxygen saturated solution led to efficient epoxidation of the 16(17)-double bond to give the 16β,17-epoxides predominantly. The observed stereoselectivity of α- to β-epoxidation ranging from 0:100 on 3, 13-di-O-acetylgibberellic acid methyl ester (7) through 11:89 on its 3,13-di-O-methoxymethyl congener, i.e., β-selectivity, was in contrast to the α-selectivity of 74:26 resulted from a peracid epoxidation on 7. This clearly illustrates the radical reaction mechanism involving an acylperoxy radical as a one-oxygen transfer species, in which the stability of the diastereomeric transition states of the intermediary α-acylperoxy carbon radical determines the stereochemical course.
