Title, Authors, Journal name: Total Synthesis of Antheliolide A. Mushti, Chandra Sekhar; Kim, Jae-Hun; Corey, E. J.. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA. Journal of the American Chemical Society (2006), 128(43), 14050-14052.

Abstract: Asym. synthesis of structurally unique marine natural product antheliolide A (I) is described. Key steps include (1) partial acetal exchange of di-Me acetal II (R = Me, Y = (CH3)2CHCH2CH2) into mixed acetal II (R = CH2CO2Me, Y = (CH3)2CHCH2CH2, III) by heating with Me glycolate in the presence of pyridinium tosylate; (2) diastereoselective [2+2] cycloaddn. of a triethylammonium salt derived from the corresponding acid of ester III, leading to IV (Y = (CH3)2CHCH2CH2) in which stereocenters were correctly established at each carbon of the four-membered ring; (3) chain extension of IV into sulfone V (Y = (CH3)2CHCH2CH2), and conversion of V into nine-membered ring VI (Y = (CH3)2CHCH2CH2) via treatment of V with MeOCOCl and DBU-mediated cyclization; (4) mild oxidative cleavage of the lactone ring in VII (Y = (CH3)2CHCH2CH2) into aldehyde VIII (Y = (CH3)2CHCH2CH2) and transformation into I. The synthesis of I has also resulted in the clarification of its abs. configuration, which had not been detd. previously.