Rearrangement of 4,5-epoxy-9-trimethylsilyldecalines. Application to the synthesis of the natural eremophilane (-)-aristolochene.
Several 4,5-epoxy-9-trimethylsilyl-eudesmanes and 15-nor-eudesmanes, having different relative stereochemistry and substitution at the oxirane ring, have been prepared starting from (-)-carvone and subjected to acid-promoted rearrangement. The presence of the silicon at C9 favors two different main reaction pathways involving C14-methyl or C1-methylene migration through the stabilization of a C10 carbocation intermediate. Selective 1,2-migration of the bridgehead methyl group takes place with trisubstituted beta-epoxide and tetrasubstituted alpha-epoxide, yielding 4-hydroxy-eremophilane and 15-nor-eremophilane compounds, while the trisubstituted alpha-epoxide suffers successive rearrangements to give a 1-hydroxy-15-nor-eremophilane through a pathway involving the initial migration of the C1 methylene. The synthetic utility of these rearrangements is shown by the synthesis of natural (-)-aristolochene.
Blay
Gonzalo
G
Departament de Química Orgànica, Facultat de Química, Universitat de València, 46100 Burjassot (València), Spain.
Cardona
Luz
L
Collado
Ana M
AM
García
Begoña
B
Pedro
José R
JR
D008968:Molecular Conformation; D009281:Naphthalenes / Q000138:chemical synthesis / Q000737:chemistry*; D012717:Sesquiterpenes / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D009281:Naphthalenes; D012717:Sesquiterpenes; C054277:aristolochene