title: Practical enantioselective process for a chiral phosphodiesterase-4 inhibitor.
abstract: L-869298 is a potent and selective phosphodiesterase-4 (PDE4) inhibitor, which is potentially useful in the treatment of asthma and chronic obstructive pulmonary disorder. A catalytic asymmetric synthesis that is suitable for the preparation of kilogram quantities of L-869298, and which does not require the use of chromatography, has been developed to support the on-going drug development program of L-869298 at Merck Research Laboratories. The catalytic asymmetric hydrogenation of an aromatic heteroaromatic ketone afforded the corresponding alcohol in almost perfect enantioselectivity. Activation of the alcohol via formation of the 4-toluenesulfonate, followed by an unprecedented displacement of the tosylate via the lithium enolate of ethyl-3-pyridyl acetate N-oxide, generated the chiral tetra-substituted ethane. The displacement reaction proceeded with inversion of configuration and without loss of optical purity. Deprotection of the displacement adduct followed by decarboxylation, afforded L-869298 in excellent overall yield. The methodology developed could be readily extended to the synthesis of several other chiral PDE4 inhibitors.
authors.affiliation: Merck Research Laboratories, Process Research, R800C367, PO Box 2000, Rahway, NJ 07065, USA. cheng_chen@merck.com
authors.forename: Cheng-Yi
authors.initials: CY
authors.lastname: Chen
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D002384:Catalysis; D003497:Cyclic N-Oxides / Q000138:chemical synthesis*; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology; D015394:Molecular Structure; D011725:Pyridines / Q000138:chemical synthesis*; D013237:Stereoisomerism; D013844:Thiazoles / Q000138:chemical synthesis
chemical_list: D003497:Cyclic N-Oxides; D004791:Enzyme Inhibitors; C475430:L 869298; D011725:Pyridines; D013844:Thiazoles; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4