Stereochemical assignment of C-24 and C-25 of amarasterone A, a putative biosynthetic intermediate of cyasterone.
A C29 phytoecdysteroid named amarasterone A (1) has been isolated from Cyathula capitata (Amaranthaceae), Leuzea carthamoides (Asteraceae), and Microsorum scolopendria (Polypodiaceae). We recently isolated amarasterone A from C. officinalis. Amarasterone A has been postulated as a biosynthetic intermediate of cyasterone in Cyathula sp. The stereochemistry at the C-24 and C-25 positions of these amarasterone A samples was investigated by comparing the NMR spectroscopic data with those of stereodefined model compounds, (24R,25S)-, (24R,25R)-, (24S,25S)-, and (24S,25R)-isomers of (20R,22R)-3β-methoxystigmast-5-ene-20,22,26-triol (2a-d), which were synthesized in the present study. Amarasterone A isolated from Cyathula officinalis was determined to be the (24R,25S)-isomer (1a), while amarasterone A from L. carthamoides was found to be the (24R,25R)-isomer (1b). Amarasterone A from M. scolopendria was found to be a mixture of 1a and 1b. The biosynthesis of cyasterone in Cyathula sp. is discussed on the basis of the identical C-24 configuration of sitosterol and amarasterone A.
Department of Chemistry and Materials Science, Tokyo Institute of Technology , Meguro, Tokyo 152-8551, Japan.
Yui
Y
Hirayama
Keiko
K
Okuzumi
Hironori
H
Masubuti
Hidehiro
H
Uekusa
Jean-Pierre
JP
Girault
Yoshinori
Y
Fujimoto
D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism; D013265:Stigmasterol / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification
C000593433:amarasterone A; C002082:cyasterone; D013265:Stigmasterol