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Cryptophycin-38 (2), -326 (3), and -327 (4) are three new trace constituents of the terrestrial cyanobacterium Nostoc sp. GSV 224. Cryptophycin-38 is a stereoisomer of cryptophycin-1 (1) and to date is the only naturally occurring analogue that possesses a S,S epoxide group in unit A. Cryptophycin-327 is a geometric isomer that differs from 1 in having a cis Delta(2)-double bond in unit A. Cryptophycin-326 is related to cryptophycin-21, but has two chlorines ortho to the methoxy group in unit B. The relative and absolute stereochemistries of 2 have been related to known cryptophycins by semisynthesis and/or spectral analysis.

Bioassay-directed fractionation of the MeCOEt extract of Crescentia cujete (Bignonaceae) resulted in the isolation of (2S,3S)-3-hydroxy-5,6-dimethoxydehydroiso-alpha-lapachone [1], (2R)-5,6-dimethoxydehydroiso-alpha-lapachone [2], (2R)-5-methoxydehydroiso-alpha-lapachone [3], 2-(1-hydroxyethyl)naphtho[2,3-b]furan-4,9-dione [4], 5-hydroxy-2-(1-hydroxyethyl)naphtho[2,3-b]furan-4,9-dione [5], 2-isopropenylnaphtho[2,3-b]furan-4,9-dione [6], and 5-hydroxydehydroiso-alpha-lapachone [7]. Compounds 1-3 are new, and all compounds are bioactive, showing selective activity towards DNA-repair-deficient yeast mutants. The isolation, structure elucidation, and biological activities of these compounds are reported.

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