Search

The West Indian alcyonacean Pseudopterogorgia bipinnata (Verrill, 1864) is shown to contain a novel bisditerpenoid ether: biskallolide A (2). The structural assignment of 2 was mainly based on 1D and 2D NMR and MS spectral data and was further confirmed by synthesis. The 2-C-alkoxylation of furanopseudopteranes kallolide A (1) and isokallolide A (8) occurs spontaneously in some solvents and involves replacement of the C2 hydroxyl with an alkoxyl group to yield solvolysis products that display net retention of configuration. The facile solvolytic 2-C-acyloxylation of kallolide A was achieved readily under similar circumstances to afford kallolide A acetate (4) as the sole product. Mechanistic details in conversion of alcohols 1 and 8 into various solvolysis products, including dimeric ethers 2 and 9, were investigated in this study. Solvolysis of kallolide A and isokallolide A in [(18)O]-labeled solvent demonstrated that the C2 alkoxyl of the solvolysis products originated from the solvent, suggesting that these conversions may proceed through an S(N)1 mechanism with generation of a carbocation intermediate. The chemical structures of kallolide A derivatives 3-7and those of isokallolide A congeners 9-11 were established by detailed analysis of the spectral data.

A chemical study of the sea feather Pseudopterogorgia bipinnata from Colombia has produced four known metabolites, namely, kallolide A (1), bipinnatin A (2), bipinnatin C (3), and bipinnatin J (4), in addition to nine previously undescribed diterpenes possessing an uncommonly high level of oxygenation. One of them, bipinnapterolide A (5), is a new representative of the pseudopterane family of diterpenes possessing the rare 2,3-epoxy-1,4-dione moiety. The other metabolites, bipinnatins G-I (6-8) and bipinnatolides F-J (9-13), are highly oxygenated cembranolide diterpenes. Their chemical structures including relative stereochemistry were established by detailed analysis of the spectral data in addition to X-ray diffraction analysis and NMR spectral comparisons with known pseudopterane and cembranolide models.

[formula: see text] A chemical study of the hexane extracts of the Caribbean gorgonian Pseudopterogorgia bipinnata (Verrill) collected in San Andrés Island, Colombia, has led to the isolation of an unprecedented heptacyclic C40 bis-diterpenoid, bisgersolanolide (1). The structure of this novel secondary metabolite, which was established by spectroscopic studies that included 2D NMR correlation methods, IR, UV, and accurate mass measurements, was confirmed by synthesis.