GALACTURONIC ACID-DERIVATIVES .8. SYNTHESIS OF N-(D-GALACTURONOYL) AMINO-ACIDS AND DIPEPTIDES

D-Galacturonic acid derivatives, amide-linked to amino acids or dipept ides, have been synthesized. These glycoconjugates exhibit stability w hen the uronic acid residue is protected with isopropylidene and acety l groups or is in its pyranoside form. The formation of the amide or p eptide linkages was best achieved by the EDCI/HOBt coupling method; an alternative method employing the 4-di-O-isopropylidene-alpha-D-galact opyranuronosyl chloride 2 furnished only moderate yields of the conjug ates. The use of NMR spectroscopy to detect racemization of the amino acid moiety is also discussed herein.