Synthesis of proline-derived dipeptides and their catalytic enantioselective direct aldol reactions: catalyst, solvent, additive and temperature effects.

A series of dipeptides of L-proline-L-amino acid and L-proline-D-amino acid were synthesized to evaluate the catalytic effect for asymmetric direct aldol reactions. In the direct aldol reaction, a catalyst of L-proline-L-amino acid achieves better enantioselectivity than the corresponding L-proline-D-amino acid catalyst. Solubility of the dipeptide catalysts in the solvents is a key point for achieving a better yield of the direct aldol reaction, while hydrogen bonding of solvent does not play an important role in attaining better enantioselectivity and yield. Yield and enantioselectivity of the direct aldol reaction in water were improved by NMM and SDS additives, but the results that were done in plain DMSO were even better.

Transesophageal echocardiographic detection of cardiac embolic source in cor triatriatum complicated by aortic saddle emboli.

Transesophageal echocardiographic findings are described in a case of cor triatriatum with atrial fibrillation complicated with cerebral and aortic saddle emboli. A spontaneous echo contrast confined to the dilated proximal chamber of the left atrium was noted and was presumed to be the embolic source in cor triatriatum.