1966 年 86 巻 10 号 p. 874-877
The NMR spectrum of domoic acid (in CF3COOH) indicates signals for a methyl at 1.43 p.p.m. (d;J=6.6 c.p.s.) and at 1.94 p.p.m. (a broad singlet), and no signal for an ethyl group. The methyl signal at 1.94 p.p.m. shows a long-range I-I coupling due to spin decoupling. The NMR spectrum of trimethyl domoate (in CDCl3) shows a doublet methyl (J=7.0 c.p.s.) at 1.29 p.p.m., a methyl signal which indicates an allylic coupling at 1.79 p.p.m., and an olefinic proton signal corresponding to 3H at 5.5∼6.6 p.p.m. From its first-order analysis, the configuration of the 1, 3-hexadienyl side chain was determined as trans : trans : S-trans. The infrared spectra of both domoic acid and trimethyl domoate show absorption due to the trans-double bond. The NMR spectrum of tetrahydrodomoic acid (in CF3COOH) shows signals for a methyl bonded to a secondary carbon at 1.12 p.p.m. (d;J=6.0 c.p.s.) and at 1.22 p.p.m. (d;J=6.6 c.p.s.). It was concluded from these observations that the structure of domoic acid would be more appropriately represented as Ls-arabo-2-carboxy-4-(1-methyl-5-carboxy-trans : trans : S-trans-1, 3-hexadienyl)-3-pyrrolidineacetic acid (VIII) rather than the previously proposed Ls-arabo-2-carboxy-4-(1-methyl-2-carboxy-1, 3-hexadieny1)-3-pyrrolidineacetic acid (I).