Activated charcoal-mediated hydroxylation under very mild conditions: conversion of physalin B into 25-hydroxyphysalin B
Abstract
Activated charcoal treatment of physalin B, a 13, 14-seco-16,24-cyclosteroidal constituent of Physalis alkekengi, in MeOH at room temperature yields a product possessing a hydroxy group at the α-position of the δ-lactone carbonyl function, namely 25-hydroxyphysalin B, in high yield.