Total synthesis of 2‐methoxy‐14‐methylpentadecanoic acid and the novel 2‐methoxy‐14‐methylhexadecanoic acid identified in the sponge agelas dispar

Abstract

The phospholipid FA composition of the Caribbean sponge Agelas dispar was revisited and 40 different FA were identified. Among these a novel 2-methoxylated FA, namely, the anteiso methyl-branched 2-methoxy-14-methylhexadecanoic acid, was identified together with the recently discovered iso methyl-branched 2-methoxy-14-methylpentadecanoic acid and the normal-chain 2-methoxytetradecanoic acid. The structures of the iso and anteiso methyl-branched 2-methoxylated FA were confirmed by total syntheses, which were accomplished in seven steps and in 45-48% overall yields. Other phospholipid FA identified in A. dispar include the unusual methyl-branched 10,13-dimethyltetradecanoic acid, 3,7,11,15-tetramethylhexadecanoic (phytanic) acid, and the 11-methyloctadecanoic acid. In addition, the delta5,9 FA (5Z,9Z)-15-methyl-5,9-hexadecadienoic acid and (5Z,9Z)-5,9-octadecadienoic acid were characterized. These findings establish alternative FA biosynthetic possibilities for these marine organisms.

Fatty Acids and Other Lipids of Marine Sponges

“…It was shown that some bacteria are able to transform phytol into 5,9,13-trimethyltridenane FA [93]; hence, this acid can originate from bacteria in sponges. 15 -+ + + + ------C 16 -+ + + + + -----C 17 ---+ + -----C 18 ---+ + + -----C 19 -----+ -----C 20 -----+ + + ---C 21 -------+ + + -C 22 -------+ + + + C 23 --------+ + + C 24 ---------+ + Note: "+"-available, "-"-not available FA [by 97].…”

“…Sponges contain branched metoxy-acids in small quantities: 2-metoxy-14-Me-16 0, 2-metoxy-14-Me-15 : 0 and 2-metoxy-14-Me-16 : 0 in the phospholipids of A. dispar [24] and 2-metoxy-13-Me-14 : 0, 2metoxy-14-Me-15 : 0, and 2-metoxy-13-Me-15 : 0 in the phospholipids of Amphimedon complanata [20].…”

Identification of Novel α‐Methoxylated Phospholipid Fatty Acids in the Caribbean Sponge Erylus goffrilleri

“…Another set of interesting a-methoxylated fatty acids in E. goffrilleri were three methyl-branched 2-methoxylated fatty acids. One of these, namely the 2-methoxy-14-methylhexadecanoic acid (2-OMe-ai-17:0) was previously described by us from an Agelas sponge [17]. However, two of these a-methoxylated methyl-branched fatty acids have not been described before in the literature.…”