Enantiodivergent biosynthesis of the dimeric sphingolipid oceanapiside from the marine sponge Oceanapia phillipensis. Determination of remote stereochemistry

The absolute stereochemistry of oceanapiside, an antifungal alpha,omega-bis -aminohydroxylipid with four stereogenic centers from the marine sponge Oce anapia phillipensis Dendy, 1895, has been obtained as 2S,3R,26R,27R from de velopment and application of a general CD method based on superposition of additive exciton couplings in perbenzoyl derivatives of bis-amino alcohols. The method allows simultaneous determination of the local relative configu ration at each of the termini of the long chain bis-aminolipid and also rel ates the absolute configuration of the two remote termini. Oceanapiside con tains erythro and three relative configurations at C1,2 and C26,27, respect ively, but opposite absolute configurations at the amino substituted carbon s C2 and C27 which implies an enantiodivergent biogenesis formally derived from both D- and L-amino acids.