New Sesquiterpenoids fromSalvia castanea Diels f.tomentosa

Abstract

Two new sesquiterpenoids, castanin A (= 4R*,5R*,5aS*,8S*,8aR*,8bR*)-8-formyl-4,5,5a,6,7,8,8a,8b-octahydro-5,8b-dihydroxy-3,5a,8-trimethyl-2-oxo-2H-indeno[4,5-b]furan-4-yl acetate; 1) and castanin B (= 1aS*,6R*,6aS*,7aR*,9aR*)-1a,2,6,6a,7a,8,9,9a-octahydro-1a,5,7a-trimethylbisoxireno[4,5 : 8,9]cyclodeca[1,2-b]furan-6-yl acetate; 2) were isolated from the aerial parts of Salvia castanea Diels f. tomentosa, together with two known compounds, oplophanone and 1β,6α-dihydroxyeudesm-4(14)-ene. Their structures were elucidated by spectroscopic analyses and, in the case of 2, also by X-ray crystallography. Castanin A (1) represents a novel sesquiterpenoid, with a contracted ring A, derived from eudesmanolide. A possible biogenetic pathway is proposed.