Soluble-Polymer-Supported Synthesis ofβ-Lactams on a Modified Poly(ethylene glycol)
作者:Rita Annunziata、Maurizio Benaglia、Mauro Cinquini、Franco Cozzi
DOI:10.1002/(sici)1521-3765(20000103)6:1<133::aid-chem133>3.0.co;2-h
日期:2000.1.3
A modified poly(ethylene glycol) (PEG) has been developed for the soluble-polymer-supported synthesis of beta-lactams. The monomethylether of PEG (MeOPEG) with an average M-W of 5000 was used as the support, a 4-(3-propyl)phenyl residue as the spacer, and a 4-oxyphenylamino group as the moiety with the reactive functionality. From this modified PEG representative aromatic, heteroaromatic, unsaturated, and aliphatic imines were obtained in high yields by different procedures. The polymer-supported imines were then employed to prepare several beta-lactams by enolate/imine condensation and ketene/imine cycloaddition. Examples of the control of the absolute stereochemistry during the azetidinone ring formation are also reported. The reactions carried out on the polymer-bound imines showed a remarkable similarity to those performed on nonimmobilized imines, both in terms of yields and stereoselectivities. Removal of the beta-lactams from the polymer has also been accomplished to directly deliver the N-unsubstituted azetidinones.