Sclerin, C_<13>H_<14>O_4, m.p. 123°, [α]_D+7.85° is a metabolite of Solerotinia libertiana, which was isolated originally as a lipase formation stimulating factor in the mycelium and later found to have the growth promoting effect for various plants. Sclerolide, C_<12>H_<14>O_4, m.p. 163° is another metabolite of the fungus obtained in minor amount. In this report the structures (3) and (32) are presented respectively for sclerin and sclerolide. The UV and IR data suggested the presence of 3-hydroxyhomophthalic anhydride structure (8) for sclerin and this was substantiated, inter alia, by following transformations. Reduction of sclerin with sodium borohydride gave (9) and (10). The methyl ether methyl ester (12) was degraded to the five-membered imide (19) by Curtius rearrangement and to the γ-lactone (20) by lead tetraacetate decarboxylation. The part structure (8) in conjunction with NMR data led to the expression (3) for sclerin. Final proof for this structure was provided by the synthesis of the nor-acid (23) derived from sclerin through the treatment with aq. 40% potassium hydroxide solution at 180°. The structure (32) for sclerolide was deduced in connection with that of sclerin and justified by the chemical correlation. Upon reduction with sodium amalgam sclerolide was converted to the lactone (20).
