Vilas Hareshwar Dahanukar

Effects of a 3-alkyl-, 4-hydroxy- and/or 8-aromatic-substituent on the phenylethanolamine N-methyltransferase inhibitor potency and α2-adrenoceptor affinity of 2,3,4,5-tetrahydro-1H-2-benzazepines

2,3,4,5-Tetrahydro-1H-2-benzazepine (THBA; 1) is nearly 100-fold more selective an inhibitor of phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) versus the alpha2-adrenoceptor than is 1,2,3,4-tetrahydroisoquinoline (THIQ; 2) (1: PNMT K(i)= 3.3 microM, alpha2-adrenoceptor K(i) = 11 microM, selectivity [alpha2 K(i)/PNMT K(i)] = 3.3; 2: PNMT K(i) = 9.7 microM, alpha2 K(i) = 0.35 microM, selectivity=0.036;). Since the PNMT inhibitory activity and selectivity of THIQ were enhanced by the introduction of a hydrophilic electron-withdrawing 7-substituent and a 3-alkyl-substituent, a similar study was conducted on THBA. 8-Nitro-THBA (3) was found to be as potent an inhibitor of PNMT as its THIQ analogue (21) and to be more selective due to its reduced alpha2-adrenoceptor affinity (3: PNMT K(i) = 0.39 microM, alpha2 K(i) = 66 microM, selectivity = 170; 21: PNMT K(i) = 0.41 microM, alpha2 K(i) = 4.3 microM, selectivity = 10). Introduction of a 3-alkyl substituent on the THBA nucleus decreased both the alpha2-adrenoceptor affinity and the PNMT inhibitory activity, suggesting an area of steric bulk intolerance at both sites. 4-Hydroxy-THBA (15), which can be considered a conformationally-restricted analogue of 3-hydroxymethyl-THIQ (30), exhibited poorer PNMT inhibitory activity and less selectivity than 30 (15: PNMT K(i) = 58 microM, alpha2 K(i) = 100 microM, selectivity = 1.7; 30: PNMT K(i) = 1.1 microM, alpha2 K(i) = 6.6 microM, selectivity = 6.0). While the addition of an 8-nitro group to 15 increased the selectivity of 16 as compared to its THIQ analogue (31), it was not as potent at PNMT nor as selective as 8-nitro-THBA (3) (16, PNMT K(i) = 5.3 microM, alpha2 K(i) = 680 microM, selectivity = 130; 31: PNMT K(i) = 0.29 microM, alpha2 K(i) = 19 microM, selectivity = 66). Compound 3 is the most selective (PNMT/alpha2) and one of the more potent at PNMT compounds yet reported in the benzazepine series, and should have sufficient lipophilicity to penetrate the blood-brain barrier (CLogP = 1.8).

Comparative molecular field analysis (CoMFA) models of phenylethanolamine N-methyltransferase (PNMT) and the α2-adrenoceptor: The development of new, highly selective inhibitors of PNMT

As a guide to the development of new and more selective inhibitors of phenylethanolamine N-methyltransferase (PNMT) vs the alpha2-adrenoceptor, we have performed a comparative molecular field analysis (CoMFA) on a series of 80 benzylamine analogues. Using the models obtained, we have proposed a series of 3-trifluoromethyl-1,2,3,4-tetrahydroisoquinolines and predicted the activity of other analogues.

Chapter 6. Synthesis of Montelukast

Montelukast sodium is an orally active selective leukotriene receptor antagonist that inhibits the cysteinyl leukotriene (CysLT1) receptor. It was developed by Merck and Company and it is currently marketed under the brand name of Singulair®. Montelukast sodium (1) is one of the most prescribed allergy drugs for the treatment of asthma in the United States with sales of about

Effect of ring size or an additional heteroatom on the potency and selectivity of bicyclic benzylamine-type inhibitors of phenylethanolamine N-methyltransferase.

4.5 billion a year (before the expiry of its patent in 2012). Merck made significant efforts to develop a commercial manufacturing process of 1. Subsequently, other generic companies also worked towards developing non-infringing and cost-effective processes for 1. However, there is scope to improve the existing synthetic strategies and one of them is to replace hazardous reagents. Replacement of hazardous reagents would help in the management of life-cycle of the drug by simplifying process and thus lowering manufacturing cost.