Shigenobu Arihara

Inokosterone, an insect metamorphosing substance from Achyranthes fauriei : Absolute configuration and synthesis☆

Abstract Inokosterone, a phytoecdysone isolated from Achyranthes fauriei (Amaranthaceae), has been partially acetylated to give the 2,26-diacetate (4) which has been converted into methyl 5 - acetoxy - 4 - methylpentanoate (7), showing no apparent [α]D, and 2β - acetoxy - 3β,14α - dihydroxy - 5β - pregn - 7 - ene - 6,20 - dione (8). Chemical and physiochemical studies have shown the configurations at C-20 and C-22 to be R. Inokosterone has thus been concluded to be a mixture of C-25 epimers of (20R,22R) - 2β,3β,14α,20,22,26 - hexahydroxy - 5β - cholest - 7 - en - 6 - one (1). After the synthesis of the model compound, a C-25 epimeric mixture of (20R,22R) - 3β,20,22,26 - tetrahydroxy - 5α - cholestane (23), inokosterone has been synthesized via (20R) - 2β,3β,14α,20 - tetrahydroxy - 20 - formyl - 5β - pregn - 7 - en - 6 - one (25) by Grignard reaction with 4 - (tetrahydrofuran - 2 - yloxy) - 3 - methylbutynylmagnesium bromide (15) followed by hydrogenation and hydrolysis. The use of an NMR shift reagent with the inokosterone acetates (9, 29) and the optical activity measurement of α - methylglutaric acid (3) derived from inokosterone have established that inokosterone is a 1:2 mixture of the C-25 R and S epimers.

Ponasteroside A, a glycoside of insect metamorphosing substance from Pteridium aquilinum var. latiusculum:: Structure and absolute configuration

Abstract A novel glycoside of an insect-metamorphosing substance, ponasteroside A, has been isolated from Pteridium aquilinum var. latiusculum (Pteridaceae). Chemical and physico-chemical properties of ponasteroside A and its hexaacetate (IV) and, in particular, its enzymatic hydrolysis into ponasterone A (II) and glucose have established the structure and absolute configuration of ponasteroside A as represented by formula 1.