5-Alkylresorcinol Derivatives from the Bryozoan Schizomavella mamillata: Isolation, Synthesis, and Antioxidant Activity

The chemical study of the bryozoan Schizomavella mamillata has led to the isolation of six new 5-alkylresorcinol derivatives, schizols A–F (1–6), whose structures were established by spectrocospic means. Schizol A (1) exhibits a (E)-6-phenylnon-5-enyl moiety linked to the C-5 of a resorcinol ring, while in schizol B (2) the substituent at C-5 contains an unusual 1,2-dihydrocyclobutabenzene moiety. Schizols C (3) and D (4) have been characterized as the 1-sulfate derivatives of 1 and 2, respectively, and schizols E (5) and F (6) are the corresponding 1,3-disulfates. Schizol A (1) has been synthetized from 3,5-dimethoxybenzaldehyde through a sequence involving a Wittig reaction for the construction of the C-1′,C-2′ bond and a Julia–Kocienski olefination for the synthesis of the C-5′,C-6′ double bond. In the ABTS (2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid)) antioxidant assay, the natural compounds schizol A (1) and schizol B (2) showed higher radical scavenging activity than the Trolox standard.