Oxazoline N-oxide mediated [2 + 3] cycloadditions. Application to a formal synthesis of (+)-carpetimycin A.
[formula: see text] Cycloaddition between gamma,delta-unsaturated beta-enamino ester 9 and camphor-derived oxazoline N-oxide 8 afforded a single adduct, 14. Dipolarophile 9 proved to be very reactive despite the substitution on the double bond. Stereoselective sodium cyanoborohydride reduction of the imminium intermediate 14a gave rise stereoselectively to beta-amino ester derivative 15a. Oxidative acidic hydrolysis, oxidation of the resulting aldehyde 18, deprotection, and cyclization afforded the beta-lactam 23, a direct precursor of (+)-carpetimycin A.
Mauduit
M
M
Laboratoire de Synthèse des Substances Naturelles, Associé au CNRS, ICMO, Université de Paris-Sud, Orsay, France.
Kouklovsky
C
C
Langlois
Y
Y
Riche
C
C
D018360:Crystallography, X-Ray; D003497:Cyclic N-Oxides / Q000737:chemistry*; D006868:Hydrolysis; D015394:Molecular Structure; D010080:Oxazoles / Q000737:chemistry*; D010084:Oxidation-Reduction; D013845:Thienamycins / Q000138:chemical synthesis*
C408867:3a,7a-dihydro-8,8-dimethyl-4,7-methanocyclohexo(1,2-d)oxazole-3-oxide; D003497:Cyclic N-Oxides; D010080:Oxazoles; D013845:Thienamycins; C030883:carpetimycin A