Structure and Computational Basis for Backbone Rearrangement in Marine Oxasqualenoids

Six novel oxasqualenoids (polyether triterpenes) were isolated from the red alga Laurencia viridis. Laurokanols A–E (1–5) comprise an unreported tricyclic core with a [6,6]-spiroketal system. Yucatecone (6) shows a biogenetically intriguing epimerization at C14. Quantum mechanical calculations were used to corroborate their structures and to explain key steps involved in the biogenetic mechanisms proposed for the formation of oxasqualenoids.This research was funded by the Spanish Ministry of Science and Innovation (PID2019-109476RB-C21), Cooperation Programme INTERREG-MAC 2014-2020 (MAC2/1.1b/279, AHIDAGRO), FEDERCB-220206 (Consejo Nacional de Ciencia y Tecnología, CONACyT), and the National Science Foundation (CHE-1856416 and supercomputing resources from the XSEDE program via CHE-030089). This study made use of the SGAI-CSIC supercomputing facilities. A.J.S.-B thanks the CajaCanarias foundation for a grantPeer reviewe