Bioorganic & Medicinal Chemistry 2013-09-01

One-pot tandem Hurtley-retro-Claisen-cyclisation reactions in the synthesis of 3-substituted analogues of 5-aminoisoquinolin-1-one (5-AIQ), a water-soluble inhibitor of PARPs.

Esther C Y Woon, Peter T Sunderland, Helen A Paine, Matthew D Lloyd, Andrew S Thompson, Michael D Threadgill

Index: Bioorg. Med. Chem. 21(17) , 5218-27, (2013)

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Abstract

Poly(ADP-ribose)polymerase-1 (PARP-1) is an important target for drug design for several therapeutic applications. 5-Aminoisoquinolin-1-one (5-AIQ) is a highly water-soluble lead compound; synthetic routes to 3-substituted analogues were explored. Tandem Hurtley coupling of β-diketones with 2-bromo-3-nitrobenzoic acid, retro-Claisen acyl cleavage and cyclisation gave the corresponding 3-substituted 5-nitroisocoumarins. Treatment with ammonia at high temperature and reduction with tin(II) chloride gave eleven target 3-substituted 5-AIQs, which were all soluble in water (>1% w/v) as their HCl salts. Most were more potent than 5-AIQ as inhibitors of PARP-1 and of PARP-2 in vitro, the most active being 5-amino-3-methylisoquinolin-1-one (PARP-1: IC50=0.23μM vs IC50=1.6μM for 5-AIQ). Some rationalisation of the SAR was achieved through molecular modelling. Copyright © 2013 Elsevier Ltd. All rights reserved.