Stereoselective reduction of alpha-bromopenicillanates by tributylphosphine.
[reaction: see text] Diastereoselective reduction of 6-bromo-6-substituted penicillanate esters has been achieved by treatment with tributylphosphine to give 6-substituted penicillanate esters. This reaction would appear to proceed through a phosphonium beta-lactam enolate species, followed by a diastereoselective protonation. This method has the advantage of being simple to carry out and it is mild, gives high diastereoselectivity, and should tolerate a number of functional groups in the substrates. Implications of these observations are discussed.
Ishiwata
A
A
Department of Chemistry, Wayne State University, Detroit, Michigan 48202-3489, USA.
Kotra
L P
LP
Miyashita
K
K
Nagase
T
T
Mobashery
S
S
D004952:Esters / Q000737:chemistry; D007769:Lactams / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010397:Penicillanic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
D004952:Esters; D007769:Lactams; D010720:Phosphines; C043255:tri-n-butylphosphine; D010397:Penicillanic Acid