Regio- and stereoselective hydroxylation of N-substituted piperidin-2-ones with Sphingomonas sp. HXN-200

Regiospecific C-H amination of (-)-limonene into (-)-perillamine by multi-enzymatic cascade reactions

BACKGROUND

(-)-Limonene, one of cyclic monoterpenes, is an important renewable compound used widely as a key building block for the synthesis of new biologically active molecules and fine chemicals. (-)-Perillamine, as derived from (-)-limonene, is a highly useful synthon for constructing more complicated and functionally relevant chemicals.

AIM

We aimed to report a more sustainable and more efficient method for the regiospecific C-H amination of (-)-limonene into (-)-perillamine.

RESULTS

Here, we report an artificial penta-enzymatic cascade system for the transformation of the cheap and easily available (-)-limonene into (-)-perillamine for the first time. This system is composed of cytochrome P450 monooxygenase, alcohol dehydrogenase and w-transaminase for the main reactions, as well as formate dehydrogenase and NADH oxidase for cofactor recycling. After optimization of the multi-enzymatic cascade system, 10 mM (-)-limonene was smoothly converted into 5.4 mM (-)-perillamine in a one-pot two-step biotransformation, indicating the feasibility of multi-enzymatic C7-regiospecific amination of the inert C-H bond of (-)-limonene. This method represents a concise and efficient route for the biocatalytic synthesis of derivatives from similar natural products.

Construction of piperidine-2,4-dione-type azaheterocycles and their application in modern drug development and natural product synthesis

The review surveys the existing routes to piperidine-2,4-dione-type heterocycles including derivatives with the most vital types of biological activity. This heterocyclic platform is ideal for the construction of modern drugs and natural products.

Evolving P450pyr monooxygenase for highly regioselective terminal hydroxylation of n-butanol to 1,4-butanediol

Directed evolution of a P450pyr created I83M/I82T mutant as the first catalyst for highly regioselective terminal hydroxylation of n-butanol to 1,4-butanediol.

Engineering of recombinant E. coli cells co-expressing P450pyrTM monooxygenase and glucose dehydrogenase for highly regio- and stereoselective hydroxylation of alicycles with cofactor recycling

E. coli (P450pyrTM-GDH) with dual plasmids, pETDuet containing P450pyr triple mutant I83H/M305Q/A77S (P450pyrTM) and ferredoxin reductase (FdR) genes and pRSFDuet containing glucose dehydrogenase (GDH) and ferredoxin (Fdx) genes, was engineered to show a high activity (12.7 U g⁻¹  cdw) for the biohydroxylation of N-benzylpyrrolidine 1 and a GDH activity of 106 U g⁻¹ protein. The E. coli cells were used as efficient biocatalysts for highly regio- and stereoselective hydroxylation of alicyclic substrates at non-activated carbon atom with enhanced productivity via intracellular recycling of NAD(P)H. Hydroxylation of N-benzylpyrrolidine 1 with resting cells in the presence of glucose showed excellent regio- and stereoselectivity, giving (S)-N-benzyl-3-hydroxypyrrolidine 2 in 98% ee as the sole product in 9.8 mM. The productivity is much higher than that of the same biohydroxylation using E. coli (P450pyrTM)b without expressing GDH. E. coli (P450pyrTM-GDH) was found to be highly regio- and stereoselective for the hydroxylation of N-benzylpyrrolidin-2-one 3, improving the regioselectivity from 90% of the wild-type P450pyr to 100% and giving (S)-N-benzyl-4-hydroxylpyrrolidin-2-one 4 in 99% ee as the sole product. A high activity of 15.5 U g⁻¹  cdw was achieved and (S)-4 was obtained in 19.4 mM. E. coli (P450pyrTM-GDH) was also found to be highly regio- and stereoselective for the hydroxylation of N-benzylpiperidin-2-one 5, increasing the ee of the product (S)-N-benzyl-4-hydroxy-piperidin-2-one 6 to 94% from 33% of the wild-type P450pyr. A high activity of 15.8 U g⁻¹  cdw was obtained and (S)-6 was produced in 3.3 mM as the sole product. E. coli (P450pyrTM-GDH) represents the most productive system known thus far for P450-catalyzed hydroxylations with cofactor recycling, and the hydroxylations with E. coli (P450pyrTM-GDH) provide with simple and useful syntheses of (S)-2, (S)-4, and (S)-6 that are valuable pharmaceutical intermediates and difficult to prepare.

Dramatic Enhancement of Enantioselectivity of Biotransformations of β-Hydroxy Nitriles Using a Simple O-Benzyl Protection/Docking Group

[Structure: see text] Catalyzed by the Rhodococcus erythropolis AJ270 whole cell catalyst, the O-benzylated beta-hydroxy alkanenitriles underwent remarkably high enantioselective biotransformations, whereas the biotransformations of free beta-hydroxy alkanenitriles gave very low enantioselectivity. The easy manipulations of O-protection and O-deprotection, excellent chemical and enantiomeric yields of biotransformations, along with the scalability render this enzymatic transformation attractive and practical for the synthesis of highly enantiopure beta-hydroxy alkanoic acids and their amide derivatives.

Cytochrome P450 alkane hydroxylases of the CYP153 family are common in alkane-degrading eubacteria lacking integral membrane alkane hydroxylases

Several strains that grow on medium-chain-length alkanes and catalyze interesting hydroxylation and epoxidation reactions do not possess integral membrane nonheme iron alkane hydroxylases. Using PCR, we show that most of these strains possess enzymes related to CYP153A1 and CYP153A6, cytochrome P450 enzymes that were characterized as alkane hydroxylases. A vector for the polycistronic coexpression of individual CYP153 genes with a ferredoxin gene and a ferredoxin reductase gene was constructed. Seven of the 11 CYP153 genes tested allowed Pseudomonas putida GPo12 recombinants to grow well on alkanes, providing evidence that the newly cloned P450s are indeed alkane hydroxylases.

Expanding the alkane oxygenase toolbox: new enzymes and applications

As highly reduced hydrocarbons are abundant in the environment, enzymes that catalyze the terminal or subterminal oxygenation of alkanes are relatively easy to find. A number of these enzymes have been biochemically characterized in detail, because the potential of alkane hydroxylases to catalyze high added-value reactions is widely recognized. Nevertheless, the industrial application of these enzymes is restricted owing to the complex biochemistry, challenging process requirements, and the limited number of cloned and expressed enzymes. Rational and evolutionary engineering approaches have started to yield more robust and versatile enzyme systems, broadening the alkane oxygenase portfolio. In addition, metagenomic approaches provide access to many novel alkane oxygenase sequences.

Enantioselective trans dihydroxylation of nonactivated C-C double bonds of aliphatic heterocycles with Sphingomonas sp. HXN-200

The bacterial strain Sphingomonas sp. HXN-200 was used to catalyze the trans dihydroxylation ofN-substituted 1,2,5,6-tetrahydropyridines 1 and 3-pyrrolines 4 giving the corresponding 3,4-dihydroxypiperidines 3 and 3,4-dihydroxypyrrolidines 6, respectively, with high enantioselectivity and high activity. The trans dihydroxylation was sequentially catalyzed by a monooxygenase and an epoxide hydrolase in the strain with epoxide as intermediate. While both epoxidation and hydrolysis steps contributed to the overall enantioselectivity in trans dihydroxylation of 1, the enantioselectivity in trans dihydroxylation of the symmetric substrate 4 was generated only in the hydrolysis of meso-epoxide 5. The absolute configuration for the bioproducts (+)-3 and (+)-6 was established as (3R,4R) by chemical correlations. Preparative trans dihydroxylation of 1a and 4b with frozen/thawed cells of Sphingomonas sp. HXN-200 afforded the corresponding (+)-(3R,4R)-3,4-dihydroxypiperidine 3a and (+)-(3R,4R)-3,4-dihydroxy pyrrolidine 6b in 96% ee both and in 60% and 80% yield, respectively. These results represent first examples of enantioselective trans dihydroxylation with nonterpene substrates and with bacterial catalyst, thus significantly extending this methodology in practical synthesis of valuable and useful trans diols. Enantioselective hydrolysis of racemic epoxide 2a with Sphingomonas sp. HXN-200 gave 34% of (-)-2a in >99% ee, which is a versatile chiral building block. Further hydrolysis of (-)-2a with the same strain afforded (-)-(3S,4S)-3a in 96% ee and 92% yield. Thus, both enantiomers of 3a can be prepared by biotransformation with Sphingomonas sp. HXN-200.