Diastereoselective Zwitterionic Aza-Claisen Rearrangement: The Synthesis of Bicyclic Tetrahydrofurans and a Total Synthesis of (+)-Dihydrocanadensolide.
J Org Chem
; 61(11): 3677-3686, 1996 May 31.
Article
in En
| MEDLINE
| ID: mdl-11667215
ABSTRACT
The zwitterionic Claisen rearrangement of optically-active N-allyl pyrrolidines and various acid chlorides proceeds with high simple diastereoselection (internal asymmetric induction) and high 1,2-asymmetric induction, generating a new C-C bond adjacent to a chiral C-O function. The resulting gamma,delta-unsaturated amides were cyclized to the corresponding optically active gamma-butyrolactones, which are useful intermediates in natural product synthesis. On one hand, a diastereoselective iodocyclization of several lactones led to tetrahydrofurans with a substitution pattern representing a key intermediate of an oxa-prostaglandin synthesis. On the other, a one-pot procedure of a Swern oxidation and consecutive Grignard reaction of one gamma-lactone allowed a diastereoselective chain elongation. The final oxidation/cyclization sequence completed a highly efficient synthesis of the (+)-dihydrocanadensolide or its C-3 epimer, respectively.
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Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
J Org Chem
Year:
1996
Type:
Article
Affiliation country:
Germany