The (9E)-oxime of erythromycin A (1) was isomerized to the (9Z)-isomer 2 in the presence of strong base. Stereospecific Beckmann rearrangement of the (9Z)-oxime led to a series of novel 8a-aza-8a-homoerythromyci active with its positional isomer azithromycin.The oxime of erythromycin A is an important intermediate in the synthesis of the clinically important macrolide antibiotics azithromycin,1a,b clarithromycin,1a,c dirithromycin1a,d and roxithromycin.1a,e Of these new compounds, azithromycin is unique in that it contains an aza substituted, ring expanded, 15-membered macrocyclic framework.2 The ring nitrogen of azithromycin is introduced by a stereospecific Beckmann rearrangement1b of erythromycin A oxime (1), which is known to exist almost exclusively in the $(9E)$ form.3 In this paper we describe the isomerization of 1 to the $(9Z)$ -erythromycin A oxime $(2)$ followed by the stereospecific transformation of 2 into novel 8a-aza-8a-homoerythromycin analogs.