Abstract
Cylindricines A−K were isolated by Blackman and co-workers from the ascidian Clavelina cylindrica collected in Tasmania. 1-3 The two main alkaloids, cylindricines A (1a) and B (2b), are readily interconvertible via an aziridinium ion intermediate.1 A 30 μM solution of the 3:2 equilibrium mixture causes significant mortality in the brine shrimp bioassay.1 Cylindricines C (1c), D (1d), E (1e), and F (1f) were isolated as minor products from these ascidians and can be prepared from the equilibrium mixture of cylindricines A and B by reaction with the appropriate nucleophile.2 Cylindricine H (1h) is the acetate of the reduction product of cylindricine F (1f), cylindricine I (1i) is the analogous isothiocyanate, and cylindricine J (2j) is a reduced isothiocyanate analogue of cylindricine B.3 Patil and co-workers recently isolated the more highly reduced thiocyanate fasicularin (3), which shows selective activity against a DNA repair-deficient organism, from the ascidian Nephteis fasicularis collected in Micronesia.