Four analogues of spiroleptosphol isolated from Leptosphaeria doliolum

Spiroleptosphol B (2), spiroleptosphol C (3), norleptosphol C (4) and hydroleptosphol (5) were isolated from ascomycete Leptosphaeria doliolum. Detailed 1H and 13C NMR spectral analyses revealed these were structural analogues of spiroleptosphol (1) which we have recently isolated from the same fungi. Spiroleptosphol B (2) carried an unprecedent 5,3-dioxatricyclo[4.4.0.11.4]undecane framework in place of the spirobicyclo ring system of 1. Spiroleptosphol C (3) was a 17-(R)-hydroxy derivative of 1. Norleptosphol C (4) was deduced to be the monocyclic structure biosynthetically resulted by decarboxylation from 3. Although 5 gave broaden 1H NMR spectrum, it was gradually transformed to 2 which suggested being a hydrolysate of 1.

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