Nicholas A. Magnus

A new asymmetric 1,4-addition method: application to the synthesis of the HIV non-nucleoside reverse transcriptase inhibitor DPC 961

Abstract The asymmetric synthesis of the HIV non-nucleoside reverse transcriptase inhibitor (NNRTI) DPC 961 is achieved in three steps with an overall yield of >55%. The asymmetry is induced by the chiral auxiliary (R)-(+)-α-methylbenzylamine, utilizing a new asymmetric 1,4-addition protocol.

Pictet-Spengler based synthesis of a bisarylmaleimide glycogen synthase kinase-3 inhibitor.

A practical synthesis of the glycogen synthase kinase-3 (GSK3) inhibitor bisarylmaleimide 1 has been accomplished employing Pictet-Spengler methodology to access the indole 7-position in preparing the benzodiazepine tricyclic fragment. A seven-step linear sequence that starts with commercially available 5-fluoroindole 7 affords the bisarylmaleimide 1 in 33% overall yield.

Additives promote Noyori-type reductions of a β-keto-γ-lactam: asymmetric syntheses of serotonin norepinephrine reuptake inhibitors.

Serotonin norepinephrine reuptake inhibitor (SNRI) pyrrolidinyl ether 2 was synthesized by employing a dynamic kinetic resolution (DKR) with enantio- and diastereoselective hydogenation on β-keto-γ-lactam 8 to afford β-hydroxy-γ-lactam 9 with 96% ee and 94% de. Reduction of 9 and purification via the dibenzoyl-(L)-tartaric acid diastereomeric salt 16 enriched the ee and de to 100%. While screening hydrogenation reaction systems with ruthenium-BINAP catalysts to prepare 9, it was found that adding catalytic HCl and LiCl enabled higher yields. In addition, the rate and equilibrium of the DKR-hydrogenation of 8 to give 9 was studied by online NMR and chiral HPLC, which indicated that one of the enantiomers of 8 was reducing faster to 9 than the equilibration of the stereocenter of 8.

Cyclization of Methyl-Coumalate-Derived Methyl 1-Benzamido-6-oxo-1,6-dihydropyridine-3-carboxylates: Assembly of the [1,2,4]Triazolo[1,5-a]pyridine Ring System

An efficient three-step synthesis of a series of fused bicyclic s-[1,2,4]triazolo[1,5-a]pyridines 1 was accomplished utilizing novel intermediates derived from inexpensive, commercially available hydrazides A and methyl coumalate B. A significant feature of this approach was the formation of a dihydrazide intermediate 2, bypassing the need for oxidative N-N bond formation in the 1,2,4-triazole synthesis. Further purification of the dihydrazides 2, beyond simple isolation, proved to be unnecessary owing to the impurity rejection afforded by the crystalline oxadiazolium salts 3. Additionally, the prepared oxadiazolium perchlorate salts showed excellent moisture stability, an unusual feature in compounds of this type.