FACILE DETERMINATION OF THE DIASTEREOISOMERIC PURITY OF 2,3-PINANEDIOL (1-CHLOROALKYL)BORONATES - ISOLATION OF BORONIC ESTERS CONTAINING A CONFIGURATIONALLY STABLE BORON

The synthesis of [1-(2-pyridylthio)alkyl]boronic esters was explored a s a means of determining the diastereoisomeric purity and the absolute configuration of the carbon alpha to the baron of the corresponding 1 -chloroalkyl derivatives. The significant nonequivalences observed in the H-1 NMR spectra of the two diastereoisomers were attributed to the presence of a strong intramolecular nitrogen-baron coordination. Rigo rous proof of a cyclic configurationally stable structure and determin ation of the boron configuration were obtained by X-ray crystallograph ic analysis. (C) 1997 Elsevier Science Ltd.