Synthesis of a beta-amino acid pharmacophore via a beta-lactam intermediate

A stereoselective synthesis of (R)-beta-amino acid 1 via a beta-lactam intermediate is discussed.     

Preparation of a clinically investigated ras farnesyl transferase inhibitor

The synthesis of ras farnesyl‐protein transferase inhibitor 1 is described on a multi‐kilogram scale. Retrosynthetic analysis reveals chloromethylimidazole 2 and a piperazinone 3 as viable precursors. The 1,5‐disubstituted imidazole system was regioselectively assembled via an improved Marckwald imidazole synthesis. A new imidazole dethionation procedure has been developed to convert the Marckwald mercaptoim‐idazole product to the desired imidazole. This methodology was found to be tolerant of a variety of functional groups providing good to excellent yields of 1,5‐disubstituted imidazoles. A new Mitsunobu cycliza‐tion strategy was developed to prepare the arylpiperazinone fragment 3 .     

CO cross-coupling of activated aryl and heteroaryl halides with aliphatic alcohols

A robust and general catalyst system facilitates the alkoxylation of activated heteroaryl halides with primary, secondary, and select tertiary alcohols without the need for an excess of either coupling partner. This catalyst system displays broad functional-group tolerance and excellent regioselectivity, and is insensitive to the order of reagent addition.     

Synthesis of a muscarinic receptor antagonist via a diastereoselective Michael reaction, selective deoxyfluorination and aromatic metal-halogen exchange reaction

An efficient synthesis of a structurally unique, novel M(3) antagonist 1 is described. Compound 1 is conveniently disconnected retrosynthetically at the amide bond to reveal the acid portion 2 and the amine fragment 3. The synthesis of key intermediate 2 is highlighted by a ZnCl(2)-MAEP complex 19 catalyzed diastereoselective Michael reaction of dioxolane 7 with 2-cyclopenten-1-one (5) to establish the contiguous quaternary-tertiary chiral centers and a subsequent geminal difluorination of ketone 17 using Deoxofluor in the presence of catalytic BF(3).OEt(2). The synthesis of the amine moiety 3 is highlighted by the discovery of a novel n-Bu(3)MgLi magnesium-halogen exchange reaction for selective functionalization of 2,6-dibromopyridine. This new and practical metalation protocol obviated cryogenic conditions and upon quenching with DMF gave 6-bromo-2-formylpyridine (26) in excellent yield. Further transformations afforded the amine fragment 3 via reductive amination with 35, Pd-catalyzed aromatic amination, and deprotection. Finally, the highly convergent synthesis of 1 was accomplished by coupling of the two fragments. This synthesis has been used to prepare multi-kilogram quantities of the bulk drug.     

Stereocontrolled preparation of a nonpeptidal (-)-spirobicyclic NK-1 receptor antagonist

The synthesis of a spirobicyclic NK-1 receptor (Substance-P) antagonist 1 antipode is described. Retrosynthetic analysis reveals an allylic halide A bearing the cyclopropoxy-substituted aryl group and a 2-phenyl-3-piperidone B. The stereochemistry in the spirobicyclic system bearing three chiral centers is initially set via a highly diastereoselective zinc-mediated coupling of the allylic bromide 23 to the optically active ketopiperidine 3. The remaining benzylic asymmetric center is set by a diastereoselective hydroboration followed by cyclization to the spirobicyclic system.     

Efficient synthesis of antiviral agent uprifosbuvir enabled by new synthetic methods

An efficient route to the HCV antiviral agent uprifosbuvir was developed in 5 steps from readily available uridine in 50% overall yield. This concise synthesis was achieved by development of several synthetic methods: (1) complexation-driven selective acyl migration/oxidation; (2) BSA-mediated cyclization to anhydrouridine; (3) hydrochlorination using FeCl₃/TMDSO; (4) dynamic stereoselective phosphoramidation using a chiral nucleophilic catalyst. The new route improves the yield of uprifosbuvir 50-fold over the previous manufacturing process and expands the tool set available for synthesis of antiviral nucleotides.

An efficient route to the HCV antiviral agent uprifosbuvir was developed in 5 steps from readily available uridine in 50% overall yield.