Halisphingosines A and B, Modified Sphingoid Bases from Haliclona tubifera. Assignment of Configuration by Circular Dichroism and van’t Hoff’s Principle of Optical Superposition

Halisphingosines A (1) and B (2), modified long-chain sphingoid bases, from the marine sponge Haliclona tubiferacollected in Brazil, were characterized after conversion to their N-Boc derivatives. The 2R,3R,6Rconfiguration of halisphingosine A, a compound first reported from Haliclonasp. from South Korea, was confirmed using a novel CD approach: deconvolution of exciton coupling from mono- and trinaphthoyl derivatives obtained by derivatization of the natural product. The sensitive CD deconvolution method, applicable to submilligram samples, simultaneously predicted the relative and absolute configuration of three stereocenters in halisphingosine A with precision and accuracy. Halisphingosine B was assigned by correlation to halisphingosine A.