Add time:07/23/2019         Source:sciencedirect.com

The cinchona alkaloid-mediated opening of prochiral cyclic anhydrides in the presence of benzyl alcohol leading to optically active hemiesters is described. Structurally diverse anhydrides are converted into their corresponding benzyl monoesters with either enantiomer being obtained with up to 99% e.e. by using quinine or quinidine as the directing additive. A simple aqueous work-up protocol permits the isolation of the products in analytically pure form and the recovery of the alkaloids almost quantitatively. These hemiesters can be converted to N-protected β-amino esters by means of Curtius degradation of the corresponding acyl azides. Subsequent cleavage of both protecting groups by a single reaction step leads to the free β-amino acids in excellent yields. The efficiency of this procedure is demonstrated by the short asymmetric synthesis of the fungicide cis-pentacin delivering the amino acid with >99.7% enantiomeric excess.

We also recommend Trading Suppliers and Manufacturers of 3-EXO-(BENZYLOXYCARBONYLAMINO)BICYCLO[2.2.1]HEPT-5-ENE-2-EXO-CARBOXYLIC ACID (cas 109853-34-1). Pls Click Website Link as below: cas 109853-34-1 suppliers