Conformational analysis of phosphorus heterocycles. Proton and phosphorus-31 nuclear magnetic resonance study of N,N'-dimethyl-(2R)-2-phospha-1,3-diazacyclohexanes
Intramolecular cyclopropanation-ring fragmentation leading to spirocyclic ring construction: a stereoselective synthesis of .beta.-chamigrene
摘要:
The transannular cyclopropanation of a keto carbene generated by Rh2(OAc)4 catalysis on a bicyclic dihydropyran nucleus provided a key oxatricyclic ketone intermediate for the synthesis of the [6.6] spirocyclic ring construction. Selective fragmentation of the cyclopropane followed by hydrolytic cleavage of the C-O bond provided the spirocyclic skeleton. Functional group manipulations to adjust oxidation states led to a total synthesis of (+/-)-beta-chamigrene in 14 steps without the use of protection/deprotection schemes.
Conformational analysis of phosphorus heterocycles. Proton and phosphorus-31 nuclear magnetic resonance study of N,N'-dimethyl-(2R)-2-phospha-1,3-diazacyclohexanes
作者:Robert O. Hutchins、Bruce E. Maryanoff、J. P. Albrand、A. Cogne、D. Gagnaire、J. B. Robert