The antibiotics vancomycin [1] (1) and everninomicin 13,384-1 [2] (for the structure, see following contribution) [3] include in their structures C3-branched 2,6-dideoxy-l-sugars containing an amino [4] or a nitro group, [5] respectively. Our interest in the total synthesis of vancomycin [6] and everninomicin 13,384-1 [7] dictated new synthetic routes to these unique sugars and methods for their attachment onto their respective target molecules. Here we report the successful attainment of both goals, culminating in the construction of key intermediates 11 and 16 (see Scheme 1) and the assembly of vancomycin disaccharide 22 (see Scheme 2). In the following communication [3] we describe the synthesis of an advanced everninomicin 13,384-1 segment incorporating the nitrosugar.
A key objective of our strategy toward the nitrogencontaining sugar units of these antibiotics was the construction of an intermediate ( 7), from which both compounds 11 and 16 could be generated (Scheme 1). Towards this goal, we envisioned a stereocontrolled anti addition [8] of an acyl anion equivalent to an aldehyde derived from l-lactic acid as a means to install the C4 stereocenter (the numbering is based on the final carbohydrate), where the functionality at C3 was projected to arise by nucleophilic chain extension of an