The Synthesis of Some Oligopeptides Derived from Novel Carbohydrate α-Amino Acids

The attempted coupling of a carbohydrate ?-azido acid with a carbohydrate ?-amino ester in the presence of a diimide, hopefully to produce a dipeptide, yielded only the carboxylic anhydride. However, the combination of 4-toluenesulfonyl chloride in pyridine was successful, and four carbohydrate dipeptides were separately produced. One of these dipeptides was further transformed into a tripeptide, and another into a hexapeptide.  A single-crystal X-ray structure is reported for (3S)-3-azido-3-C-carboxy-3-deoxy-1,2:5,6-di-O-isopropylidene-?-d-ribo-hexose, amide with (3S)-3-amino-3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-methoxycarbonyl-?-d-ribo-hexose.