| 2,4(5)-Disubstituted imidazoles are synthesized from both acyloins and olefins. The products of subsequent N-alkylation, predominantly 1,2,4-trisubstitution, are treated with singlet oxygen. The resulting dehydrodiamides are hydrogenated with a chiral catalyst to yield > 90% enatiomerically pure diamides/dipeptides. C-alkylation of 1,4-disubstituted imidazoles is also studied. Part B concerns the protection of anomeric centers in saccharides with (beta)-trimethylsilylethanol and the protection of diols with derivatives of p-methoxyacetophenone. |
