3.4.4- Trisubstituted-2-azetidinones

Optically pure c/.v-2-azetidi none-tethered dienes have been reported to undergo intermolecular Diels-Alder reaction with a variety of symmetric and unsymmetric dienophiles [257] providing a synthetic entry to various types of racemic and homochiral 1,3,4-trisubstituted 2-azetidinones (I, Fig. 7). 

Alcaide and coworkers have reported in 2002 the synthesis of various types of racemic and homochiral 1,3,4-trisubstituted- or fused polycyclic (3-lactams (III and IV, respectively, Fig. 9) via intermolecular 1,3-dipolar cycloaddition reaction of 2-azetidinone-tethered nitrones with a variety of alkenes or alkynes [264]. 

The Diels-Alder cycloaddition reaction of both cis- and trans-dienyl-2-azetidi-nones with unsymmetrical dienophiles in the presence of Lewis acid catalysts has been reported to give in regio-, stereo-, and remarkably high 7i-facial selectivity novel l,3,4-trisubstituted-2-azetidinone derivatives in good yields (I and II, Fig. 26), [306],... 

The obtained results have shown that the trisubstituted (3-lactams a-e of Fig. 50 exhibited some antiviral activity, slightly higher than that reported for the prototype 2-azetidinone la of Fig. 49. No appreciable influence of the absolute configuration, either at the C4 or at the 1-phenylethyl substituent, on the inhibition of viral replication, was observed. The presence of an aromatic group at the 1-acyl... 

An azetidinone carrying vicinal alkene and alkyne groups, one of which may be an N-substituent, on the four-membered ring may be cyclized in the presence of a trisubstituted tin hydride at elevated temperature (Scheme 9) <1999JOC5377, 2003JOC3106>. In this way, the 1,4-disubstituted /3-lactams 303 were converted into the fused bicyclics 304 in moderate yield. 

Barton, D H R, Gateau-Oleska, A, Anaya-Mateos, J, Cleophax, J, Gero, S D, Chiaroni, A, Riche, C, Asymmetric synthesis of 1,3,4-trisubstituted and 3,4-disubstituted 2-azetidinones strategy based on use of D-glucosamines as a chiral auxiliary in the Staudinger reaction, J. Chem. Soc. Perkin. Trans. 1, 3211-3212, 1990. 

Trisubstituted 2-azetidinones have been prepared by diastereoselective and jr-facially selective Lewis acid-catalyzed intermolecular Diels-Alder reactions of 3-butadienylazetidin-... 

The stereoselective synthesis of vinyl ethers is accomplished by N -(arylidene (or alkylidene) amino) - 2-azetidinones reaction with ozone and NaBH treatment resulting in di- and trisubstituted olefins derivatives [78],... 

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