Caulerspiros A and B, a new pair of α-tocopheroid isomers from the green alga Caulerpa racemosa var. turbinata

Caulerspiros A (1) and B (2), a new pair of α-tocopheroid isomers, with five known compounds (3-7) were isolated from the green alga Caulerpa racemosa var. turbinata. Their structures were elucidated by the method of comprehensive spectroscopy. The absolute configurations of 1 and 2 were established by the methods of ECD calculation and comparing with the previously reported literature. Compounds 1 and 2 represented the rare examples of α-tocopherol derivatives possessing a core unit of 1-oxaspiro[4.4]non 7-en-6-one. Additionally, the antibacterial activities of these seven compounds were also evaluated. However, none of them showed antibacterial activities with MIC values > 128 μg/ml.