SYNTHESIS AND REACTIONS OF O-ACETYLATED BENZYL ALPHA-GLYCOSIDES OF 6-O-(2-ACETAMIDO-2-DEOXY-BETA-D-GLUCOPYRANOSYL)-N-ACETYLMURAMOYL-L-ALANYL-D-ISOGLUTAMINE ESTERS - THE BASE-CATALYZED ISOGLUTAMINE REVERSIBLE GLUTAMINE REARRANGEMENT IN PEPTIDOGLYCAN-RELATED STRUCTURES