The development of a safe, robust process for the preparation of ravuconazole (1), an antifungal agent, is described. The discovery and development of procedures enabling the efficient synthesis of multikilogram quantities of 1 and the process demonstration through plant scale preparations are presented. A controlled means to prepare a Grignard reagent and utilization of Fourier Transform Infrared spectroscopy (FTIR) monitoring to safely conduct the reaction is featured.
A practical synthesis of the SGLT-2 inhibitor β-C-aryl-D-glucoside (1) has been developed. The route employed 2,3,4,6-tetra-O-trimethlysilyl-D-glucano-1,5-lactone as the key chiral building block, prepared efficiently from the commercially available, inexpensive raw materials, D-gluconolactone and trimethylsilyl chloride. The salient step in the synthesis is the Lewis acid-mediated stereoselective reduction of a methyl C-aryl peracetylated glycoside using a silyl hydride to set the stereochemistry of the crucial anomeric chiral center. Several novel cocrystalline complexes of 1 with L-phenylalanine and L-proline were discovered. Single-crystal structures of these complexes and several synthetic intermediates have been determined. The Lphenylalanine complex was developed and used to purify and isolate the API. All steps were implemented at multikilogram scale.
We report research and development conducted to enable the safe implementation of a highly enantioselective palladium-catalyzed desymmetrization of a meso−bis-ester using trimethylsilylazide (TMSN 3 ) as the nucleophile. This work is used as a case example to discuss safe practices when considering the use of azide reagents or intermediates, with a focus on the thermodynamic and quantitative analysis of the hazards associated with hydrazoic acid (HN 3 ).
The search for a faster, safer protocol for the direct synthesis of 5-aryltetrazoles from aryl nitriles in the presence of sodium azide and an amine hydrochloride salt led to the discovery of a buffered system comprised of BnNH 2 , BnNH 2 •HCl, and NaN 3 . After optimization of reaction conditions and a thorough investigation of reaction safety, the procedure was demonstrated for the synthesis of several hundred grams of 4-chloro-2-(2Htetrazol-5-yl)phenol. The generality of the developed reaction conditions was established by a small-scale reactivity screen using 16 additional aryl and heteroaryl nitrile substrates.
A concise bulk synthesis of stereochemically complex CCR2 antagonist BMS-741672 is reported. A distinct structural feature is the chiral all-cis 1,2,4-triaminocyclohexane (TACH) core, which was assembled through consecutive stereocontrolled heterogeneous hydrogenations: efficient Pt-catalyzed reduction of a β-enaminoester, directed by (S)-αmethylbenzylamine as a low-cost chiral template, and reductive amination of a 3,4-cis-disubstituted cyclohexanone over sulfided Pt/C introduced a tert-amine, setting the third stereocenter in the all-cis cyclohexane core. The heterogeneous catalysts were recycled. Ester hydrolysis produced a γ-amino acid, isolated as its Na salt. A challenging Curtius reaction to introduce the remaining C−N bond at C-2 was strongly influenced by the presence of the basic tert-amine, providing a stereoelectronically highly activated isocyanate. Detailed mechanistic and process knowledge was required to enable clean trapping with an alcohol (t-BuOH) while avoiding formation of side products, particularly an unusual carbamoyl phosphate. Deprotection, N-acetylation, and uncatalyzed S N Ar coupling with known 4-chloroquinazoline provided the final product. The resulting 12-step synthesis was used to prepare 50 kg of the target compound in an average yield of 82% per step.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.