Progressive-Convergent Elucidation of Stereochemistry in Complex Polyols.The Absolute Configuration of(-)-Sagittamide A

摘要

The structure of(-)-sagittamide A(1),an unprecedented polyacetoxy,long-chain alpha,omega-dicarboxylic acid isolated from a tropical didemnid tunicate,was solved by application of conventional 2D NMR spectroscopic methods;however,only partial stereochemistry could be assigned.Although configurations of the terminal amino acids(L-ornithine and L-valine)were determined readily by conventional methods,the contiguous 5,6,7,8,9,10-hexol hexaacetate in 1 represented a significantly more complex NMR problem,in part,because of isolated stereohexad C5-C10 flanked by CH_2 groups and equivocal interpretations of J coupling.