Enantioselective Synthesis of Nelfinavir via Asymmetric Bromocyclization of Bisallylic Amide.

We describe a concise enantioselective synthesis of the HIV-protease inhibitor nelfinavir (1) via a new route in which the key step is construction of the central optically active 1,2-amino alcohol framework via asymmetric bromocyclization of bisallylic amide with N-bromosuccinimide in the presence of a catalytic amount of ( S)-BINAP or ( S)-BINAP monoxide. The remaining alkene and bromo functionalities were used to install the requisite thioether and chiral perhydroisoquinoline units, respectively.

Synthesis of new thienyl ring containing HIV-1 protease inhibitors: promising preliminary pharmacological evaluation against recombinant HIV-1 proteases.

A series of new thienyl ring containing analogues of nelfinavir and saquinavir with different substitution patterns were synthesized from suitable enantiopure diols. Their inhibitory activity against wild type recombinant HIV-1 protease was evaluated. In general thienyl groups spaced from the core by a methylene group gave products showing IC(50) in the nanomolar range, irrespective of the type and the substitution pattern of the heterocycle. The range of activity of the two most active compounds is substantially maintained or even increased against two commonly selected mutants, under drug pressure, such as V32I and V82A.

Asymmetric synthesis of the potent HIV-protease inhibitor, nelfinavir.

An asymmetric synthesis of nelfinavir is described starting from acrolein and (S)-methyl phenyl sulfoxide. The key features include (a) stereoselective preparation of a beta-protected amino-gamma,delta-unsaturated sulfoxide by the reaction of an alpha-sulfinyl carbanion with an unsaturated t-butyl sulfinylimine, (b) stereoselective bromohydrin formation using the pendant sulfoxide group as an intramolecular nucleophile, and (c) use of commercially or readily prepared inexpensive starting materials.

What happened: the chemistry side of the incident with EMS contamination in Viracept tablets.

A technical review of the events leading to the global recall of Viracept film coated tablets 250 mg in June 2007 is given from the drug substance manufacturing perspective. Root cause analysis performed and corrective actions implemented are presented. Using the decay rate of ethyl methane sulfonate in Viracept film coated tablets 250 mg at 25 degrees C derived from stability studies, establishing of the worst case scenario for patient exposure to ethyl methane sulfonate, is outlined. Whereas the first evaluation based on ethyl methane sulfonate levels found in the drug substance suggested a worst case patient exposure of 2300 ppm, the decay rate of ethyl methane sulfonate in the drug product and the time gap between drug product manufacture and earliest possible use by patients led to the conclusion that 920 ppm (+/-10%) over a period of approx. 90 days is a reasonably cautious assumption for the worst case patient exposure scenario.

[Novel synthesis and spectral characterization of nelfinavir].

An efficient and environmentally friendly procedure for the one-pot synthesis of (3S,4aS,8aS)-2-((2R,3R)-3-amino-2-hydroxy-4-(phenylthio)butyl)- N-tert -butyl-decahydroisoquinoline-3-carboxamide(VII), the intermediate of nelfinavir, was described, and activating ester was applied to getting nelfinavir(IX). Under the catalysis of potassium hydroxide, benzyl (R)-1-((S)-oxiran-yl)-2-(phenylthio) ethyl carbamate was obtained(IV) in methanol. Then IV and (3S,4aS,8aS)- N-tert -butyl-decahydroisoquinoline-3-carboxamide(V) were refluxed in methanol until the reaction was finished. Potassium hydroxide(w(KOH) = 40%) in water was added to remove benzyloxycarbonyl group in water bath with a yield of 89.0%. 3-acetoxy-2-methylbenzoic acid-succinimide ester(II) reacted with VII and acetyl group was removed by dense aqueous ammonia, giving nelfinavir(IX). The vibrations of functional groups of thiIIs compound corresponding to the main infrared absorption peaks were discussed. The molecular ion and quasi molecular ion peaks were obtained via MALDI-TOF MS, and 1H NMR and 13CNMR shifts of this compound were assigned by means of DEPT(distortionless enhancement by polarization transfer spectrum), HMBC(1H detected heteronuclearmultiple bond correlation spectrum), HSQC(1H detected heteronuclear single-quantum coherence spectrum) and DQF-COSY(double-quantum filtered-correlated spectroscopy). The results provided useful information for structure characterization and quality control of nelfinavir.

Prodrugs of HIV protease inhibitors-saquinavir, indinavir and nelfinavir-derived from diglycerides or amino acids: synthesis, stability and anti-HIV activity.

With the aim of improving the pharmacological properties of current protease inhibitors (PIs), the synthesis of various acyl and carbamate amino acid- or diglyceride-containing prodrugs derived from saquinavir, indinavir and nelfinavir, their in vitro stability with respect to hydrolysis and their anti-HIV activity in CEM-SS and MT4 cells have been investigated. l-Leucine (Leu) and l-phenylalanine (Phe) were connected through their carboxyl to the PIs while l-tyrosine (Tyr) was conjugated through its aromatic hydroxyl via various spacer units. Hydrolysis of the prodrug with liberation of the active free drug was crucial for antiviral activity. The Leu- and Phe-PI prodrugs released the active free drug very rapidly (half-lives of hydrolysis in buffer at 37 degree C of 3-4 h). The Tyr-PI conjugates with a -C(O)(CH(2))(4)- linker exhibited half-lives in the 40-70 h range and antiviral activities in the 21-325 nM range (from 2 to 22 nM for the free PIs). The chemically very stable carbamate "peptidomimetic" Tyr-PI prodrugs (no hydrolysis detected after 7 days in buffer) displayed a very low anti-HIV activity or were even inactive (EC(50) from 2300 nM to >10 microM). A very low antiviral activity was measured for the diglyceride-substituted saquinavir and for all of the disubstituted indinavir and nelfinavir prodrugs. All these prodrugs probably released the active parent PI too slowly under the antiviral assay conditions. These results combined with those from transepithelial transport studies (Rouquayrol et al., Pharm. Res., 2002, 19, 1704-1712) indicate that conjugation of amino acids (through their carboxyl) to the PIs constitutes a most appealing alternative which could improve the intestinal absorption of the PIs and reduce their recognition by efflux carriers.

A process in need is a process indeed: scalable enantioselective synthesis of chiral compounds for the pharmaceutical industry.

This report deals with enantioselective synthesis of viracept 1 (nelfinavir mesylate, AG 1343), a potent HIV protease inhibitor, and 3-hydroxytetradecanoic acid 3, a component of lipid A comprising lipopolysaccharide embedded in the cell surface of Gram-negative bacteria, from both strategic and practical perspectives. As regards the synthesis of 1, the synthetic approaches to its central intermediate 2 possessing the common structural motif of 1,4-differentially substituted-2-amino-3-hydroxylbutane are mainly discussed with emphasis on the molecular symmetry that has helped streamline the synthetic strategy. In the discussion of the synthetic strategies to access a single enantiomer of 3, the chiral methodologies that have been applied so far are assessed for industrial viability; the synthetic alternatives explored include resolution via diastereomeric salt formation, lipase-catalyzed kinetic resolution, asymmetric synthesis, and chiral pool approaches.

Design and synthesis of a conformationally restricted trans peptide isostere based on the bioactive conformations of saquinavir and nelfinavir.

The design and synthesis of a new peptide isostere which contains a trans alkene core is described. The key step involves a Wadsworth-Emmons reaction between chiral aldehyde (2S)-9a and chiral phosphonate 7 under base-sensitive conditions to give a chiral enone (2R)-24a which was reduced to afford the desired trans alkene isosteres (2R,5R)-6a and (2R,5S)-6b (Scheme 6). A potential application of this isostere in the synthesis of HIV protease inhibitors is also discussed.

Copper-mediated cross-coupling of aryl boronic acids and alkyl thiols.

[reaction: see text] The cross-coupling of aryl boronic acids and alkanethiols mediated by copper(II) acetate and pyridine in anhydrous dimethylformamide affords aryl alkyl sulfides in good yield with a wide variety of substituted aryl boronic acids. The method is applicable to the synthesis of aryl sulfides of cysteine.

Viracept (nelfinavir mesylate, AG1343): a potent, orally bioavailable inhibitor of HIV-1 protease.

Using a combination of iterative structure-based design and an analysis of oral pharmacokinetics and antiviral activity, AG1343 (Viracept, nelfinavir mesylate), a nonpeptidic inhibitor of HIV-1 protease, was identified. AG1343 is a potent enzyme inhibitor (Ki = 2 nM) and antiviral agent (HIV-1 ED50 = 14 nM). An X-ray cocrystal structure of the enzyme-AG1343 complex reveals how the novel thiophenyl ether and phenol-amide substituents of the inhibitor interact with the S1 and S2 subsites of HIV-1 protease, respectively. In vivo studies indicate that AG1343 is well absorbed orally in a variety of species and possesses favorable pharmacokinetic properties in humans. AG1343 (Viracept) has recently been approved for marketing for the treatment of AIDS.