to H-12, including 9-Me, with a diagnostic COSY correlation between H-7 and H-12 indicating the presence of a cyclohexyl ring. HMBC correlations from H-14 to C-12, C-13 and 13-Me, and from H-12 to C-13, 13-Me and C-14 confirmed C-13 as the shared point of attachment of the cyclohexyl ring and the pentaene-containing chain. Additional HMBC correlations from H-4 to C-5, C-6, C-12, C-13 and 13-Me, from H-6 to C-4, C-5 and C-12, and from H-14 to C-4 defined a decalin ring system fused at C-7 and C-12, and containing a ∆ 5,6 double bond. Next, HMBC correlations from H-4, H-6 and a putative methoxy group at δH 3.59 (3H, s) to δC 166.3 positioned a carboxylic acid methyl ester at C-5. Finally, HMBC correlations from H-2 and 3-Me to C-4 and from H-2 to C-1 (δC 167.1) confirmed the presence of a 3substituted but-2-enoic acid side chain attached at C-4. The relative configuration of the trans-decalin system was established by detailed analysis of the 1 H-1 H ROESY spectrum of 1 (Fig. ), with diagnostic correlations between H-4, H-7, H-9, H-10a, H-11b and 13-Me on the top face, and between H-10b and H-12 on the bottom face (Fig. ). Unfortunately, attempts at crystallising 1 to determine the absolute configuration of the molecule were unsuccessful. However, we have tentatively assigned a 24R,25R configuration based on detailed genomic analysis (discussed below).