title: Quirogane, prenopsane, and patzcuarane skeletons obtained by photochemically induced molecular rearrangements of longipinene derivatives.
abstract: Ultraviolet irradiation of (1R,3S,4S,5S,10R,11R)-1-acetyloxy-7-oxolongipin-8-ene (6), prepared from longipinene diesters isolated from Stevia salicifolia, afforded the new quirogane (7) and prenopsane (8) derivatives, as the major products, together with the minor secondary photoproduct (1R,3R,5R,8S,11S)-1-acetyloxy-7-oxopatzcuar-9-ene (9), which possesses a novel tricyclic sesquiterpene skeleton. The stereostructures of the new compounds 7-9 were mainly determined by NMR techniques including COSY, HSQC, HMBC, and NOESY in combination with molecular modeling obtained by density functional theory calculations. A reaction mechanism accounting for the observed transformations is proposed.
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000 Mexico.
authors.forename: Myriam
authors.initials: M
authors.lastname: Meléndez-Rodríguez
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Cerda-García-Rojas
authors.forename: Pedro
authors.initials: P
authors.lastname: Joseph-Nathan
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010777:Photochemistry; D012717:Sesquiterpenes / Q000737:chemistry*; D013057:Spectrum Analysis; D036625:Stevia / Q000737:chemistry*
chemical_list: D012717:Sesquiterpenes; C468588:patzcuarane; C468587:prenopsane; C468589:quirogane; C410907:longipinene