Bunsho Makino

Physalins N and O from Physalis alkekengi

Abstract The structures of physalins N and O, isolated from Physalis alkekengi var. francheti , were determined as 7α-hydroxyphysalin B and (25 S )-25,27-dihydrophysalin A, respectively.

New physalins possessing an additional carbon-carbon bond from Physalis alkekengi var. francheti

Abstract Physalins R and S were isolated from Physalis alkekengi var. francheti and their structures were determined by spectroscopic studies as 15α-hydroxy-11β,15β-cyclo-15-deoxophysalin B and 3α,5α-cyclo-6β-hydroxy-2,3,5,6-tetrahydrophysalin B, respectively. The UV-irradiation of physalin B afforded physalin R, and this photo-induced C(11)-C(15) bond formation was shown to be sensitized intramolecularly by the conjugated enone group in the A ring.

The Structure of Physalin T from Physalis alkekengi var. francheti

Abstract A new steroidal constituent named physalin T (3) was isolated from the aqueous extract of Physalis alkekengi var. francheti. Based on 1H and 13C NMR spectral studies the structure was assigned as 2,3-dihydrophysalin D, i.e., 5α,6β-dihydroxy-2,3,5,6-tetrahydrophysalin B, which is the first example of a natural physalin possessing a saturated ring A moiety. The structure was confirmed by the chemical transformation from the known physalin D (2) to physalin T.

Upon ‘physalin L’ isolated from Physalis minima

5α-Ethoxy-6β-hydroxy- and 6β-ethoxy-5α-hydroxy-5,6-dihydrophysalin B were derived from the corresponding 5β,6β- and 5α,6α-epoxides, respectively, by acid treatment in ethanol. The 5α-ethoxy derivative was isolated as an artefact from Physalis alkekengi, while other workers isolated the 6β-ethoxy compound as a constituent of P. minima and mistakenly named it as physalin L, which had already been assigned to (25S)-3,4-didehydro02,3,25,27- tetrahydrophysalin A. The 1H NMR spectrum of the 6β-ethoxy derivative prepared by us, however, did not agree with the reported data.

Activated charcoal-mediated hydroxylation under very mild conditions: conversion of physalin B into 25-hydroxyphysalin B

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.