NEW SIALYLTRANSFERASE INHIBITORS BASED ON CMP-QUINIC ACID - DEVELOPMENT OF A NEW SIALYLTRANSFERASE ASSAY

Quinic acid (4) was transformed into phosphitamides 6, 14, and 15, whi ch could be readily linked to 5'-O-unprotected cytidine derivative 7; ensuing oxidation of the obtained phosphite triesters with tert-butylh ydroperoxide furnished the corresponding phosphate triesters 8, 16, an d 17, respectively. Hydrogenolytic debenzylation of the phosphate moie ty, base catalysed removal of acetyl protective groups, and basic hydr olysis of the methylester of the quinic acid moiety furnished CMP-Neu5 Ac analogues 1-3. In order to measure their inhibition of sialyltransf erases, a nonradioactive sialyltransferase assay [employed for alpha(2 -6)-sialyltransferase from rat liver (EC 2.4.99.1)] based on reversed- phase HPLC separation of UV-labelled acceptor 20 (p-nitrophenyl glycos ide of N-acetyllactosamine) from the UV-labelled product 21 (p-nitroph enyl glycoside of sialyl alpha(2-6')-N-acetyllactosamine) and p-nitrop henylalanine as internal standard was developed. The assay reproduced the reported K-M values for CMP-Neu5Ac and N-acetyllactosamine and the K-i values for CDP. 1 and 2 turned out to be potent sialyltransferase inhibitors.