High fidelity: 1‐Iodoalkynes react rapidly and selectively with organic azides in the presence of copper(I) catalysts (see scheme; TTTA=tris((1‐tert‐butyl‐1H‐1,2,3‐triazolyl)methyl)amine). The reaction is compatible with many functional groups and solvents, and 5‐iodotriazole products were usually obtained in excellent yield. These products can be further functionalized to give fully substituted 1,2,3‐triazoles.

Building from the results of a computational screen of a range of triazole-containing compounds for binding efficiency to human immunodeficiency virus type 1 protease (HIV-1-Pr), a novel series of potent inhibitors has been developed. The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), which provides ready access to 1,4-disubstituted-1,2,3-triazoles, was used to unite a focused library of azide-containing fragments with a diverse array of functionalized alkyne-containing building blocks. In combination with direct screening of the crude reaction products, this method led to the rapid identification of a lead structure and readily enabled optimization of both azide and alkyne fragments. Replacement of the triazole with a range of alternative linkers led to greatly reduced protease inhibition; however, further functionalization of the triazoles at the 5-position gave a series of compounds with increased activity, exhibiting Ki values as low as 8 nM.

Infections with the diarrheagenic pathogen, Giardia lamblia, are commonly treated with the 5-nitroimidazole (5-NI) metronidazole (Mz), and yet treatment failures and Mz resistance occur. Using a panel of new 2-ethenyl and 2-ethanyl 5-NI derivatives, we found that compounds with a saturated bridge between the 5-NI core and a pendant ring system exhibited only modestly increased antigiardial activity and could not overcome Mz resistance. By contrast, olefins with a conjugated bridge connecting the core and a substituted phenyl or heterocyclic ring showed greatly increased antigiardial activity without toxicity, and several overcame Mz resistance and were more effective than Mz in a murine giardiasis model. Determination of the half-wave potential of the initial oneelectron transfer by cyclic voltammetry revealed that easier redox activation correlated with greater antigiardial activity and capacity to overcome Mz resistance. These studies show the potential of combining systematic synthetic approaches with biological and electrochemical evaluations in developing improved 5-NI drugs.

Sauber verklebt: 1‐Iodalkine reagieren schnell und selektiv mit organischen Aziden in Gegenwart von Kupfer(I)‐Katalysatoren [siehe Schema; TTTA=Tris((1‐tert‐butyl‐1H‐1,2,3‐triazolyl)methyl)amin]. Viele funktionelle Gruppen und Lösungsmittel können verwendet werden, und die 5‐Iodtriazole, die in sehr guten Ausbeuten entstehen, lassen sich gut zu vollständig substituierten 1,2,3‐Triazolen funktionalisieren.

The long held notion that hexenyl radicals bearing large substituents on the radical carbon cyclize to give 1,2-trans-substituted cyclopentanes is experimentally disproved by study of the radical cyclization of an assortment of simple and complex substrates coupled with careful product analysis and rigorous assignment of configurations. X-ray studies and syntheses of authentic samples establish that the published assignments for cis- and trans-1-tert-butyl-2-methylcyclopentane must be reversed. The original assignment based on catalytic hydrogenation of 1-tert-butyl-2-methylenecyclopentane was compromised by migration of the double bond prior to hydrogenation. The cyclization of 1-tert-butylhexenyl radical is moderately cis selective, and the selectivity is increased by geminal substitution on carbon 3. This selectivity trend is general and extends to relatively complex substrates. It has allowed Ihara to reduce the complexity of an important class of round trip radical cyclizations to make linear triquinanes to the point where two tricyclic products-cis-syn-cis and cis-anti-cis-account for about 80% of the products. However, the further increase in selectivity that was proposed by lowering the temperature is shown to be an artifact of the analysis methods and is not correct. This work solidifies "1,2-cis selectivity" in cyclizations of 1-subsituted hexenyl radicals as one of the most general stereochemical trends in radical cyclizations.

During the process of developing a synthesis to a complex molecule, multiple decisions are made regarding the strategies and tactics used to prepare key bonds. In this article, we preface a series of papers describing the development of the commercial synthesis of BMS-663068 (a potential new treatment for HIV), with an in-depth discussion of the important strategic decisions made during the process of designing and demonstrating the proposed commercial synthesis of this complex clinical candidate. We discuss the key strategic disconnections and the key experimental data used to drive our tactical decisions during development. In the remaining articles in this series, we outline the development of these enabling chemical processes into scalable procedures ready to support commercialization of this promising new medicine.

The development of two enabling routes that led to the production of >1000 kg of BMS-663068 (3) is described. The route identified for the initial 100 kg delivery to support development activities and initial clinical trials involved the conversion of 2-amino-4-picoline to the parent active pharmaceutical ingredient (API), followed by pro-drug installation and deprotection. To eliminate the problematic isolation of the parent API and synthesis of di-t-butyl(chloromethyl)phosphate, a second-generation pro-drug installation route was developed which involved the conversion of a late-stage common intermediate to an N(1)-thioether derivative followed by chloromethylation, displacement with di-t-butylpotassium phosphate, and deprotection. This second strategy resulted in the multikilogram scale preparation of the API in 14 linear steps and ∼7% overall yield.

During the development of a Friedel–Crafts acylation for the preparation of a key pyrrole intermediate in the synthesis of the HIV attachment inhibitor, BMS-663068-03, a significant scale dependence was found. A precipitous drop in yield was observed for the acylation of a protected pyrrole with chloroacetyl chloride upon scale-up. Spectroscopic studies to mitigate this scale dependence led to the identification of the complex effect of dissolved hydrogen chloride (HCl) as well as the poor reactivity of the acylating agent, chloroacetyl chloride. At this point, the counterintuitive choice to switch to a longer, but scale-independent, three-step route was made. By changing the acylating agent to acetyl chloride, a more robust process was obtained. Rapid development of a high yielding α-chlorination then provided the common α-chloroketone intermediate required to generate the desired α-amide ketopyrrole. The improved yield and scalability of this three-step process supported the addition of one linear step to the route, and it was demonstrated successfully at scale.