Enzymatic Desymmetrization Research Articles

An enzymatic route to the synthesis of tricyclic fused hexahydrofuranofuran P2-Ligand for a series of highly potent HIV-1 protease inhibitors

We describe a stereoselective synthesis of an optically active (1R, 3aS, 5R, 6S, 7aR)-octahydro-1,6-epoxy-isobenzo-furan-5-ol derivative. This stereochemically defined heterocycle serves as a high-affinity ligand for a variety of HIV-1 protease inhibitors. The key synthetic steps involve a highly enantioselective enzymatic desymmetrization of meso-1,2(dihydroxymethyl)cyclohex-4-ene and conversion of the resulting optically active alcohol to a methoxy hexahydroisobenzofuran derivative. A substrate controlled stereoselective dihydroxylation afforded syn-1,2-diols. Oxidation of diol provided the substituted 1,2-diketone and L-Selectride reduction provided the corresponding inverted syn-1,2-diols. Acid catalyzed cyclization furnished the ligand alcohol in optically active form.

Die Totalsynthese von Isoxeniolid A**

AbstractIsoxeniolid A ist ein hochgespanntes marines Diterpenoid aus der Familie der Xenicane. Es steht repräsentativ für eine Unterfamilie von Xenicanen, deren 9‐gliedriger Ring eine allylische Hydroxygruppe aufweist; derartige Xenicane wurden bisher nicht als Zielmoleküle von Totalsynthesen verfolgt. Wir beschreiben hier die erste asymmetrische Totalsynthese eines derartigen Xenicans, nämlich des Isoxeniolid A. Dabei lag der Schlüssel zum Aufbau des besonders herausfordernden E‐konfigurierten Cyclononenrings in einer diastereoselektiven intramolekularen Nozaki–Hiyama—Kishi‐Reaktion. Andere wichtige Transformationen waren eine enzymatische Desymmetrisierung zur Kontrolle der absoluten Stereochemie, eine diastereoselektive Cuprat‐Addition und die Verwendung eines bifunktionalen Vinylsilan‐Bausteins. Unsere Synthesestrategie ermöglicht auch den Zugang zur enantiomeren Form des Naturstoffs sowie prinzipiell zu einer Vielzahl anderer natürlicher Xenicane und synthetischer Analoga für Struktur‐Aktivitäts‐Untersuchungen.

Total Synthesis of Isoxeniolide A.

Isoxeniolide A is a highly strained xenicane diterpenoid of marine origin. This natural product is representative for a subfamily of xenicanes incorporating an allylic hydroxy group in the nine-membered ring; members of this xenicane subfamily so far have not been targeted by total synthesis. Herein, we describe the first asymmetric total synthesis of isoxeniolide A. Key to forming the challenging E-configured cyclononene ring was a diastereoselective intramolecular Nozaki-Hiyama-Kishi reaction. Other important transformations include an enzymatic desymmetrization for absolute stereocontrol, a diastereoselective cuprate addition and the use of a bifunctional vinyl silane building block. Our strategy also permits access to the enantiomer of the natural product and holds potential to access a multitude of xenicane natural products and analogs for structure-activity relationship studies.

Synthetic studies towards volvalerenol A: access to a fully functionalized cycloheptane framework in an asymmetric fashion through the exploitation of C2-symmetry.

The enantioselective synthesis of a fully functionalized cycloheptane core of the naturally occurring triterpenoid volvalerenol A, exhibiting pseudo-C2 symmetry, was achieved. Enantioselective enzymatic desymmetrization (EED), asymmetric methallylation, and reductive ring opening of an cyclopropane overbred intermediate were the key reactions to access the cycloheptanone core. Further synthetic manipulations, via a unique "MPV" (Meerwein-Ponndorf-Verley) type reductive ring-opening of an epoxide and other synthetic transformations, afforded two fully functionalized cycloheptane frameworks of the target molecule.

Enantioselective Formal Synthesis of (–)-Catharanthine through Enzyme-Catalyzed Desymmetrization of a meso-Azabicyclo [2.2.2]octane

AbstractIboga-type indole alkaloids are a promising compound group of potentially effective drugs. The common indole-fused pentacyclic skeleton is composed of an isoquinuclidine, and both enantiomers of this architecture are naturally present. In this study, we used enzymatic desymmetrization to obtain an optically active isoquinuclidine possessing four chiral carbon centers from a prochiral diester in one step. In addition, we synthesized a pentacyclic intermediate for catharanthine in an enantioenriched form through the late-stage construction of the common Iboga scaffold.

Proteases: An overview on its recent industrial developments and current scenario in the revolution of biocatalysis

In recent years there is tremendous growth in the utilization of alkaline protease as an industrial catalyst. The extensive usage of chemicals for various applications in industries is usually associated with severe health effects and environmental problems. In this context, the scientific world mainly aims to substitute these toxic compounds with healthy environmental benign products for a good life. So, the chemicals are replaced by various enzymes among which microbial enzymes especially proteases are mostly employed in the modern corporate sectors in the manufacture of detergents, leather, food products and also in waste management techniques. The present review summarizes the various industrial applications of alkaline protease, different factors influencing its production like isolation source, optimum pH, temperature, the effect of inhibitor and metal ions on alkaline protease producing microorganisms. Furthermore the biocatalytic activity of alkaline protease in various organic transformations namely Knoevenagel condensation, Domino reaction, Aldol reaction, transesterification reaction, resolution of amino acids in organic solvents, kinetic resolution of carboxylic acids, strained amides, peptide synthesis by alcalase cross-linked enzyme aggregates (CLEA), enantioselective hydrolysis of prochiral dinitril, enzymatic desymmetrization of Ganciclovir, enantioselective aminoacid ester hydrolysis and fragmentation of p-amido benzyl ethers have been compiled in the current review.

P-Chiral Phosphine Sulfide Synthesis by Combination of Enzymatic Desymmetrization and Successive Deformylative P–C Cross-Couplings

AbstractA process for the synthesis of P-chiral triarylphosphine sulfides via sequential Pd-catalyzed stereospecific P–C coupling reactions of P-chiral precursors prepared by enzymatic desymmetrization was developed. Three independent aryl substituents could be introduced onto the P atom by the sequential P–C couplings under mild conditions while retaining the high enantiopurity.

Design, Synthesis and X-Ray Structural Studies of Potent HIV-1 Protease Inhibitors Containing C-4 Substituted Tricyclic Hexahydro-Furofuran Derivatives as P2 Ligands.

The design, synthesis, X-ray structural, and biological evaluation of a series of highly potent HIV-1 protease inhibitors are reported herein. These inhibitors incorporate novel cyclohexane-fused tricyclic bis-tetrahydrofuran as P2 ligands in combination with a variety of P1 and P2' ligands. The inhibitor with a difluoromethylphenyl P1 ligand and a cyclopropylaminobenzothiazole P2' ligand exhibited the most potent antiviral activity. Also, it maintained potent antiviral activity against a panel of highly multidrug-resistant HIV-1 variants. The corresponding inhibitor with an enantiomeric ligand was significantly less potent in these antiviral assays. The new P2 ligands were synthesized in optically active form using enzymatic desymmetrization of meso-diols as the key step. To obtain molecular insight, two high-resolution X-ray structures of inhibitor-bound HIV-1 protease were determined and structural analyses have been highlighted.

Enzymatic Desymmetrisation of Prochiral Phosphines and Phosphine P-Sulfides as a Route to P-Chiral Catalysts

The enzyme-catalyzed monoacetylation of prochiral bis (2-hydroxymethylphenyl)methylphosphine and bis (2-hydroxymethylphenyl)phenylphosphine and their P-sulfides gave, in one single step, as a result of desymmetrisation, the corresponding monoacetates in moderate yields and with an enantiomeric excess of 16 to 98%, depending on the substrate structure and enzyme applied. The absolute configurations of the selected products were determined by a chemical correlation. This led to the conclusion that, in the case of phosphines, phosphine oxides and phosphine sulfides enzymes preferentially produce compounds of the same spatial arrangement. The new compounds obtained will be transformed into chiral catalysts/ligands.

Desymmetric hydrolysis of prochiral imide for S-pregabalin synthesis by rationally designed d-hydantoinase

A one-step enzymatic desymmetrization process was developed to produce the direct chiral precursor for S-pregabalin synthesis with high yield and high eep value.

Stereoselective synthesis of novel carbocyclic and heterocyclic scaffolds of medicinal importance from biocatalytically derived enantiopure α-substituted-β-hydroxy esters

Biocatalytically derived enantiopure α-substituted-β-hydroxy esters can act as a potential precursor for the stereoselective synthesis of a diverse set of small organic molecules of medicinal importance. Chiral γ-Z-butenolides can be constructed through a “Pd–Cu” bimetallic cascade cyclization. Synthetic anti-viral compound 5′-methylaristeromycin was accessed through RCM (ring closing metathesis) and nucleophilic opening of epoxide with nucleobase adenine. Structurally novel enantiopure cyclitol analogs were synthesized efficiently through RCM reaction, enzymatic desymmetrization, and cyclopropanation reaction starting from the same precursor. Chiral cyclic γ-keto-ester was accessed by exploration of asymmetric Stetter reaction from the same starting material. Finally, novel bicyclic enones can also be synthesized through RCM/Robinson annulation sequence. All the synthesized compounds can be potentially useful in medicinal chemistry research.

Enantioselective Total Synthesis of (+)‐Nordasycarpidone, (+)‐Dasycarpidone, and (+)‐Uleine

AbstractThe structure of uleine type alkaloids is characterized by the presence of a bridged tetracyclic hexahydro‐1H‐1,5‐methanoazocino[4,3‐b]indole ring system 1. Various strategies have been developed to access this polycyclic structural motif. We report herein a one‐step conversion of appropriately functionalized 1,3,4‐trisubstituted cyclopent‐1‐ene to 1 by way of an integrated oxidation/reduction/cyclization (iORC) process. This domino sequence, initiated by oxidative cleavage of cyclopentene ring, generated subsequently a cyclohexenone, an indole and a 1,3‐bridged piperidine ring through formation of one C−C and two C−N bonds. Compound 1 is subsequently converted to nordasycarpidone, dasycarpidone and uleine. The chirality of the molecule was introduced by enzymatic desymmetrization of commercially available meso cis‐3,5‐diacetoxy‐1‐cyclopentene.

Kinetics of enzyme-catalysed desymmetrisation of prochiral substrates: product enantiomeric excess is not always constant.

The kinetics of enzymatic desymmetrisation were analysed for the most common kinetic mechanisms: ternary complex ordered (prochiral ketone reduction); ping-pong second (ketone amination, diol esterification, desymmetrisation in the second half reaction); ping-pong first (diol ester hydrolysis) and ping-pong both (prochiral diacids). For plausible values of enzyme kinetic parameters, the product enantiomeric excess (ee) can decline substantially as the reaction proceeds to high conversion. For example, an ee of 0.95 at the start of the reaction can decline to less than 0.5 at 95% of equilibrium conversion, but for different enzyme properties it will remain almost unchanged. For most mechanisms a single function of multiple enzyme rate constants (which can be termed ee decline parameter, eeDP) accounts for the major effect on the tendency for the ee to decline. For some mechanisms, the concentrations or ratios of the starting materials have an important influence on the fall in ee. For the application of enzymatic desymmetrisation it is important to study if and how the product ee declines at high conversion.

Development of a Synthesis Process for a Novel HCV NS5A Inhibitor, Emitasvir

A new approach to the synthesis of Emitasvir (DAG181), a small molecule hepatitis C virus (HCV) nonstructural protein 5A (NS5A) inhibitor, is described. Enantioselective enzymatic desymmetrization ...

Asymmetric synthesis of intermediate for (1R,2S)-ethyl 1-amino-2-vinylcyclopropanecarboxylate by desymmetrization using engineered esterase from Bacillus subtilis

(1R,2S)-Ethyl 1-amino-2-vinylcyclopropanecarboxylate (VCPA), is a key intermediate for anti-hepatitis C virus drugs. In this study, we developed an efficient manufacturing method of intermediate for (1R,2S)-VCPA by enzymatic desymmetrization of a malonate diester derivative. In synthesis scheme of VCPA (1S,2S)-1-(ethoxycarbonyl)-2-vinylcyclopropanecarboxylic acid (VCPME) is the monoester intermediate, which is converted from 2-vinylcyclopropane-1,1-dicarboxylate diethyl ester (VCPDE). As a result of esterase screening for producing (1S,2S)-VCPME from VCPDE by enzymatic desymmetrization, p-nitrobenzyl esterase from Bacillus subtilis NBRC3027 (PNBE3027) showed high enantioselectivity (more than 90% e.e.). Based on the homology model of PNBE3027, a library of mutants with the substitution of L70, L270, L273, and L313 in substrate-binding pocket was created for improvement in enantioselectivity. (1S,2S)-VCPME produced by the best variant harboring L70D, L270Q, L273R, and L313M showed 98.9% e.e. of enanthiopurity. Furthermore, preparative scale production of (1S,2S)-VCPME using the quadruple mutant was achieved. Our investigations present a new efficient process for (1R,2S)-VCPA using esterase and diverse to be applied for the industrial scale production.

Building Complexity and Achieving Selectivity through Catalysis – Case Studies from the Pharmaceutical Pipeline

The last decade of small-molecule process development has witnessed a trend of increasing molecular complexity for clinical candidates. The continued advance of novel catalytic methods and subsequent translation to efficient and scalable processes has enabled process chemists to overcome the challenges associated with increasing complexity. This Account highlights several examples from the process chemistry laboratories at Amgen.1 Introduction2 The Evolution of Molecular Complexity3 Catalysis as a Lever to Build Complexity4 Ru(II)-Catalyzed Dynamic Kinetic Resolution Enabling the Manufacture of AMG 2325 Application of Enzymatic Desymmetrization toward Scale-Up of the MCL-1 Inhibitor AMG 1766 Synthesis of Fucostatin 1: Catalytic Asymmetric Transfer Hydrogenation7 Manganese-Catalyzed Asymmetric Epoxidation To Prepare a Carfilzomib Intermediate8 Asymmetric Reduction Strategies: Novel Apelin Receptor Agonists and AMG 9869 Conclusions

Definitive Screening Design Optimization of Chemoenzymatic Process for (R)‐3‐(Carbamoylmethyl)‐5‐methylhexanoicacid: A Key Intermediate of Pregabalin

AbstractA practical scalable chemoenzymatic process was developed for the synthesis of (R)‐3‐(carbamoylmethyl)‐5‐methylhexanoic acid (2) (R‐CMHA) and achieved 98.5% ee and 99% HPLC purity at pilot scale. The systematic statistical design of experimentation (DOE) of esterification, enzymatic desymmetrization and CaCl2 assisted amidation led to the robust design space.

Structure-Based Design of Highly Potent HIV-1 Protease Inhibitors Containing New Tricyclic Ring P2-Ligands: Design, Synthesis, Biological, and X-ray Structural Studies.

We describe here design, synthesis, and biological evaluation of a series of highly potent HIV-1 protease inhibitors containing stereochemically defined and unprecedented tricyclic furanofuran derivatives as P2 ligands in combination with a variety of sulfonamide derivatives as P2' ligands. These inhibitors were designed to enhance the ligand-backbone binding and van der Waals interactions in the protease active site. A number of inhibitors containing the new P2 ligand, an aminobenzothiazole as the P2' ligand and a difluorophenylmethyl as the P1 ligand, displayed very potent enzyme inhibitory potency and also showed excellent antiviral activity against a panel of highly multidrug-resistant HIV-1 variants. The tricyclic P2 ligand has been synthesized efficiently in an optically active form using enzymatic desymmetrization of meso-1,2-(dihydroxymethyl)cyclohex-4-ene as the key step. We determined high-resolution X-ray structures of inhibitor-bound HIV-1 protease. These structures revealed extensive interactions with the backbone atoms of HIV-1 protease and provided molecular insights into the binding properties of these new inhibitors.

Progress toward a Convergent, Asymmetric Synthesis of Jervine.

Progress toward a convergent approach for the enantioselective synthesis of the Veratrum alkaloid jervine is presented. The two requisite fragments were stereoselectively and efficiently fashioned from economical and readily available reagents. Key reactions include (a) a highly diastereoselective Ireland-Claisen rearrangement to establish the necessary cis-relationship between the amine and methyl group on the tetrahydrofuran E-ring; (b) a diastereoselective selenoetherification reaction that enabled the assembly of the D/E oxaspiro[4.5]decene in the needed configuration; and (c) an enzymatic desymmetrization of an abundant achiral diol en route to a key four-carbon building block as a practical alternative to a protected Roche ester reduction.

Synthesis of a CGRP Receptor Antagonist via an Asymmetric Synthesis of 3-Fluoro-4-aminopiperidine.

A practical and efficient enantioselective synthesis of the calcitonin gene-related peptide receptor antagonist 1 has been developed. The key structural component of the active pharmaceutical ingredient is a syn-1,2-amino-fluoropiperidine 4. Two approaches were developed to synthesize this important pharmacophore. Initially, Ru-catalyzed asymmetric hydrogenation of fluoride-substituted enamide 8 enabled the synthesis of sufficient quantities of compound 1 to support early preclinical studies. Subsequently, a novel, cost-effective route to this intermediate was developed utilizing a dynamic kinetic asymmetric transamination of ketone 9. This synthesis also features a robust Ullmann coupling to install a bis-aryl ether using a soluble Cu(I) catalyst. Finally, an enzymatic desymmetrization of meso-diester 7 was exploited for the construction of the γ-lactam moiety in 1.