Chemoenzymatic synthesis of piperoxan, prosympal, dibozane, and doxazosin

A review on Arthrobacter sp. lipase: A versatile biocatalyst for the kinetic resolution to access enantiomerically pure/enriched compounds

Over the last few years, there has been a dramatic increase in the number of reports related to Arthrobacter sp. lipase (ABL:MTCC No. 5125) catalyzed kinetic resolution performed in biphasic media. A strain displaying esterase/lipase activity and designated as ABL was isolated, during the course of a screening program at Indian Institute of Integrative Medicine, Jammu. Considerable research has shown that reactions catalyzed by ABL are more selective than many commercial lipases. Since new applications of this lipase are emerging, there is a great need to provide all the relevant information exclusively. This review article is an attempt to cover all the relevant reports based on isolation, purification, immobilization, and application of ABL in the biopharmaceutical sector.

A versatile catalyst system for enantioselective synthesis of 2-substituted 1,4-benzodioxanes

We report the synthesis of enantiomerically enriched 1,4-benzodioxanes containing alkyl, aryl, heteroaryl, and/or carbonyl substituents at the 2-position. The starting 1,4-benzodioxines were readily synthesized via ring closing metathesis using an efficient nitro-Grela catalyst at ppm levels. Excellent enantioselectivities of up to 99:1 er were obtained by using the versatile catalyst system [Ir(cod)Cl]2/BIDIME-dimer in the asymmetric hydrogenation of 2-substituted 1,4-benzodioxines. Furthermore, DFT calculations reveal that the selectivity of the process is controlled by the protonation step; and coordinating groups on the substrate may alter the interaction with the catalyst, resulting in a change in the facial selectivity.

Enantioselective Access to Chiral 2-Substituted 2,3-Dihydrobenzo[1,4]dioxane Derivatives through Rh-Catalyzed Asymmetric Hydrogenation

Rh-catalyzed asymmetric hydrogenation of various benzo[ b][1,4]dioxine derivatives was successfully developed to prepare chiral 2-substituted 2,3-dihydrobenzo[1,4]dioxane derivatives using ZhaoPhos and N-methylation of ZhaoPhos ligands with high yields and excellent enantioselectivities (up to 99% yield, >99% enantiomeric excess (ee), turnover number (TON) = 24 000). Moreover, this asymmetric hydrogenation methodology, as the key step with up to 10 000 TON, was successfully applied to develop highly efficient synthetic routes for the construction of some important biologically active molecules, such as MKC-242, WB4101, BSF-190555, and ( R)-doxazosin·HCl.

Dual photoredox and nickel-catalyzed desymmetric C–O coupling reactions: visible light-mediated enantioselective synthesis of 1,4-benzodioxanes

Chiral 2,2′-bipyridine ligands are key to success in an enantioselective desymmetric C–O cross coupling reaction via dual visible light photoredox and nickel catalysis, resulting in chiral 1,4-benzodioxanes under mild reaction conditions.

Synthesis of Ofornine mimics from natural product l-vasicine as anti-hypertensive agents

We report the chemical synthesis of Ofornine mimics from l-vasicine, structure-activity relationship studies and their in vivo screening for anti-hypertensive action in Wistar rats. It was observed that most of the analogs possessed anti-hypertensive effect; however, the duration of the effect was variable and mostly transient. The results demonstrated that the analogs 12, 13, 14, 15, and 16 showed a sharp and significant decrease in systolic and diastolic blood pressure for 30-60min after intravenous administration. Analog (S)-(3-hydroxypyrrolidin-1-yl)(2-(pyridin-4-ylamino)phenyl)methanone (8) showed a significant decrease in blood pressure in a dose dependent manner whose maximal response lowered to 79.29±4.26mmHg of SBP and 62.55±2.9 of DBP at 10mg/kg intravenous dose. Further, the significant anti-hypertensive effect of 8 lasted for about 2.5h at 10mg/kg dose. We also evaluated the acute toxicity of the analog 8 as per the OECD guidelines and the compound was found to be safe up to the dose of 2000mg/kg body weight. These preclinical findings suggest that the analog 8 could be considered as a promising lead and a durable anti-hypertensive drug candidate and deserves further investigation. The SAR studies clearly showed that the amide, hydroxyl and pyridine ring plays important role in showing the activity.

Recent Advances in Lipase-Mediated Preparation of Pharmaceuticals and Their Intermediates

Biocatalysis offers an alternative approach to conventional chemical processes for the production of single-isomer chiral drugs. Lipases are one of the most used enzymes in the synthesis of enantiomerically pure intermediates. The use of this type of enzyme is mainly due to the characteristics of their regio-, chemo- and enantioselectivity in the resolution process of racemates, without the use of cofactors. Moreover, this class of enzymes has generally excellent stability in the presence of organic solvents, facilitating the solubility of the organic substrate to be modified. Further improvements and new applications have been achieved in the syntheses of biologically active compounds catalyzed by lipases. This review critically reports and discusses examples from recent literature (2007 to mid-2015), concerning the synthesis of enantiomerically pure active pharmaceutical ingredients (APIs) and their intermediates in which the key step involves the action of a lipase.

From 2-aminomethyl-1,4-benzodioxane enantiomers to unichiral 2-cyano- and 2-carbonyl-substituted benzodioxanes via dichloroamine

2-Substituted 1,4-benzodioxanes, such as 2-cyano-, 2-methoxycarbonyl-, 2-aminocarbonyl-, and 2-formyl-1,4-benzodioxane, are key synthons that for the most part are never described as enantiomers or are inadequately characterized for enantiomeric purity. They were prepared by quantitative N,N-dichlorination of (R)- and (S)-2-aminomethyl-1,4-benzodioxane and successive functional group conversions in high yields without any racemization of the stereogenic benzodioxane C(2).

Synthesis of single-enantiomer bioactive molecules: a brief overview

Chiral-center enantiomers have been shown to differ significantly in biological activity, pharmacodynamics, pharmacokinetics and toxicity. New developments in the stereoselective organic synthesis have enriched the vast literature of synthetic methodologies applicable to access natural products as well as bioactive molecules. These compounds also include new drugs, drug candidates and reagents used to explore biological processes. The article reviews the synthesis of optically pure drugs, biologically active intermediates and amino alcohols by using different methods.