Recent advance of chemoenzymatic catalysis for the synthesis of chemicals: Scope and challenge

Chemoenzymatic catalysis can give full play to the advantages of versatile reactivity of chemocatalysis and excellent chemo-,regio-,and stereoselectivities of biocatalysis.These chemoenzymatic methods can not only save resource,cost,and operating time but also reduce the number of reaction steps,and avoid separating unstable intermediates,leading to the generation of more products under greener circumstances and thereby playing an indispensable role in the fields of medicine,materials and fine chemicals.Although incompatible challenges between chemocatalyst and biocatalyst remain,strategies such as biphasic system,artificial metalloenzymes,immobilization or supramolecular host,and protein engineering have been designed to overcome these issues.In this review,chemoenzymatic catalysis according to different chemocatalysis types was classifiably described,and in particular,the classic dynamic kinetic resolutions(DKR)and cofactor regeneration were summarized.Finally,the bottlenecks and development of chemoenzymatic catalysis were summarized,and future development was prospected.

Chemoenzymatic Synthesis of an Enantiomerically Enriched Bicyclic Carbocycle Using <i>Candida parapsilosis</i>ATCC 7330 Mediated Enantioselective Hydrolysis

Enantiomerically enriched (R)-1-(2-bromocycloalkenyl)-3-buten-1-ol and its derivatives were obtained via enantioselective hydrolysis [resolution] with good enantioselectivities (E = 31 to >500) using Candida parapsilosis ATCC 7330. The various reaction parameters were optimized for enantioselective hydrolysis to achieve high enantiomeric excess (ee) and conversions. Among the substrates tested, (RS)-1-(2-bromocyclohex-1-en-1-yl) but-3-yn-1-yl acetate was hydrolysed by the biocatalyst in 12 h to the corresponding (R)-alcohol in 49% conversion and >99 ee. The optically pure allylic alcohol thus obtained was used as a chiral starting material for the synthesis of an enantiomerically enriched bicyclic alcohol effectively establishing achemoenzymatic route.

Magnetic wrinkled organosilica-based metal-enzyme integrated catalysts for enhanced chemoenzymatic catalysis

Core-shell structured magnetic wrinkled organosilica-based metal-enzyme integrated catalysts were synthesized,and their catalytic performances were studied in the chemoenzymatic dynamic kinetic resolution of chiral amines in an organic solvent,as well as in the chemoenzymatic synthesis of chiral alcohols in water.Structureperformance studies revealed the important influence of their tunable structure and composition on the optimization of activity,stability,and recyclability in chemoenzymatic catalysis.

Total synthesis of dansyl and biotin functionalized ganglioside GM3 by chemoenzymatic method

Ganglioside GM3, as well as other gangliosides, offers a variety of modifications in its sialic acid and ceramide moieties GM3 exhibits various types of important biological activities, due to the inability to effectively observe the trafficking of ganglioside GM3, developing sensitive research tools for specific monitoring of GM3 expression and activity is thus desirable. The total synthesis of a dansyl and biotin bifunctionalized fluorescent ganglioside GM3 were reported in this article. From lactose after 13 reaction steps, the compound of 2′ -biotinoylaminoethyl-6-N-dansylamido-6-deoxy-β-D-galatopyranosyl-(1→4)-β-D-glucopy-ranoside was obtained in total yield of 16.2%. Sialylation of dansyl and biotin functionalized lactose by enzymatic method gave dansyl and biotin labeled ganglioside GM3. The fluorescent property of this compound was also investigated.

Chemoenzymatic synthesis of α2–3-sialylated carbohydrate epitopes

Sialic acids are common terminal carbohydrates on cell surface.Together with internal carbohydrate structures,they play important roles in many physiological and pathological processes.In order to obtain α2–3-sialylated oligosaccharides,a highly efficient one-pot three-enzyme synthetic approach was applied.The P.multocida α2–3-sialyltransferase (PmST1) involved in the synthesis was a multifunctional enzyme with extremely flexible donor and acceptor substrate specificities.Sialyltransferase acceptors,including type 1 structure (Galβ1–3GlcNAcβProN3),type 2 structures (Galβ1–4GlcNAcβProN3 and 6-sulfo-Galβ1– 4GlcNAcβProN3),type 4 structure (Galβ1–3GalNAcβProN3),type 3 or core 1 structure (Galβ1–3GalNAcβProN3) and human milk oligoscaccharide or lipooligosaccharide lacto-N-tetraose (LNT) (Galβ1–3GlcNAcβ1–3Galβ1–4GlcβProN3),were chemically synthesized.They were then used in one-pot three-enzyme reactions with sialic acid precursor ManNAc or ManNGc,to synthesize a library of naturally occurring β2–3-linked sialosides with different internal sugar structures.The sialylated oligosaccharides obtained are valuable probes for their biological studies.

A chemoenzymatic cascade with the potential to feed the world and allow humans to live in space

While the typical targets of(chemo-)enzymatic cascades are fine chemicals(e.g.,pharmaceuticals),a chemoen-zymatic cascade,artificial starch anabolic pathway(ASAP),was recently developed to synthesize starch from CO_(2).The key results and outstanding features of ASAP are discussed here.We envision that ASAP and its mi-crobial counterpart may enable efficient synthesis of food and sequestration of CO_(2)in a circular manner,thus contributing to a sustainable and hunger-free world and future habitation in space.

Microbial Transformation of Taxoids and Synthesis of Taxoids with an Oxetane Ring

Microbial trdrisformation of taxoids was inveStigared: taxoid 2 was transformed into 1β and 14β hydroxylated derivahves 3 and 4, unnatural taxoid 6 was transformed into 1β-hydroxy derivative 7 and 11(15-1) abeotaxane 8. Taxoids with an oxetane ring, 11-13 were synthesized from 1 via chemical reachons.

Practical Synthesis of Valbenazine via 1,3-Dipolar Cycloaddition

Comprehensive Summary,Valbenazine(Ingrezza),a potent and highly selective inhibitor of vesicular monoamine transporter type 2(VMAT2)through the active metabolite hydrotetrabenazine(HTBZ),has been approved for the treatment of tardive dyskinesia and,very recently,for chorea,which is associated with Huntington's disease.Despite numerous synthetic efforts dedicated to the synthesis of HTBZ,the industrial preparation of valbenazine uses dihydroisoquinoline as a starting material and the chiral resolution of racemic HTBZ derived from ketone reduction.Herein,we present a practical synthesis of HTBZ and valbenazine featuring a highly stereoselective 1,3-dipolar cycloaddition and enzymatic kinetic resolution.The cascade process includes cycloaddition,N—O bond cleavage,and lactamization,which proved to be operationally simple.The allure of the enzymatic resolution developed in this work offers a rapid access toward affording tetrahydroisoquinoline(THIQ)-fused piperidine in the production of medically significant compounds,such as yohimbine and reserpine.

Glycosylation engineering of therapeutic IgG antibodies： challenges for the safety, functionality and efficacy

Glycosylation of the Fc region of IgG has a profound impact on the safety and clinical efficacy of therapeutic antibodies. While the biantennary complex.type oligosaccharide attached to Asn297 of the Fc is essen- tial for antibody effector functions, fucose and outer-arm sugars attached to the core heptasaccharide that gen- erate structural heterogeneity （glycoforms） exhibit unique biological activities. Hence, efficient and quan- titative glycan analysis techniques have been increas- ingly important for the development and quality control of therapeutic antibodies, and g｜ycan profiles of the Fc are recognized as critical quality attributes. In the past decade our understanding of the influence of glycosy- lation on the structure/function of IgG-Fc has grown rapidly through X-ray crystallographic and nuclear magnetic resonance studies, which provides possibili- ties for the design of novel antibody therapeutics. Fur- thermore, the chemoenzymatic glycoengineering approach using endoglycosidase-based glycosyn- thases may facilitate the development of homogeneous IgG glycoforms with desirable functionality as next- generation therapeutic antibodies. Thus, the Fc glycans are fertile ground for the improvement of the safety,functionality, and efficacy of therapeutic IgG antibodies in the era of precision medicine.

Peptide asparaginyl ligases——renegade peptide bond makers

Making peptide bonds is tightly controlled by genetic code and machinery which includes cofactors,ATP,and RNAs.In this regard,the stand-alone and genetic-code-independent peptide ligases constitute a new family of renegade peptide-bond makers.A prime example is butelase-1,an Asn/Asp(Asx)-specific ligase that structurally belongs to the asparaginyl endopeptidase family.Butelase-1 specifically recognizes a C-terminal Asx-containing tripeptide motif,Asn/Asp-Xaa-Yaa(Xaa and Yaa are any amino acids),to form a site-specific Asn-Xaa peptide bond either intramolecularly as cyclic proteins or intermolecularly as modified proteins.Our work in the past five years has validated that butelase-1 is a potent and versatile ligase.Here we review the advances in ligases,with a focus on butelase-1,and their applications in engineering bioactive peptides and precision protein modifications,antibody-drug conjugates,and live-cell labeling.

Exploiting Complex-Type N-Glycan to Improve the in Vivo Stability of Bioactive Peptides

Peptides can be potentmolecules with high efficacy and selectivity in the development of biotherapeutics.However,the poor pharmacokinetic properties of peptides pose major challenges for their broader medicinal applications.Inspired by the proteinstabilizing role of natural N-glycosylation,we design and synthesize a series of parathyroid hormone(PTH)peptides(1-34),bearing either N-GlcNAc or biantennary complex-type N-glycan modification,and evaluate their serum stability and biological activities.The results indicate that an N-Asn-linked complex-type sialylundecasaccharide can increase the serum half-life and in vivo bioactivity of PTH peptides with a broad tolerance of modification sites.Further,hydrogen/deuterium exchange mass spectroscopy indicates that the larger-sized Nglycan can induce enhanced hydration dynamics in its surroundings,which may facilitate an improved resistance for the peptide against enzymatic proteolysis.This sialylundecasaccharide-based peptideengineering strategy has also been applied to glucagon-like peptide-1(7-37),leading to glycopeptides with enhanced hypoglycemic activity and acting time in vivo.Together,these results demonstrate the potential of using sialylated complextype N-glycan as a general engineering strategy for developing long-acting peptide therapeutics.

The thiamine-dependent enzyme of the vitamin K biosynthesis catalyzes reductive C-N bond ligation between nitroarenes and α-ketoacids

The thiamine-dependent enzyme （1R, 2S, 5S, 6S）-2-succinyl-5-enolpyruvyl-6-hydroxyl-3-cyclohexene-l-carboxylate （SEPHCHC） synthase, also known as MenD, catalyzes a Stetter-like reaction in the biosynthesis of vitamin K. It is found to catalyze a novel reductive C-N bond ligation reaction between nitroarenes and et-ketoacids to form N-hydroxamates. This reaction likely pro- ceeds through an enzyme-mediated, slow two-electron reduction of the nitroalkanes to form a nitroso intermediate, which serves as the electrophilic acceptor of the ketoacid-derived acyl anion. The involvement of the nitroso intermediate is support- ed by the fact that similar N-hydroxamates are readily formed at a much higher rate when nitroso compounds replace the nitro substrates in the chemoenzymatic reactions. These results demonstrate that the thiamine-dependent enzyme is able to catalyze novel, nonnative reactions that may find new chemoenzymatic applications.

Bioengineered production of glycosaminoglycans and their analogues

Glycosaminoglycans(GAGs)are a class of linear polysaccharides,consisting of alternating disaccharide sequences of uronic acid and hexosamines(or galactose)with and without sulfation.They can interact with various proteins,such as growth factors,receptors and cell adhesion molecules,endowing these with various biological and pharmacological activi-ties.Such activities make GAGs useful in health care products and medicines.Currently,all GAGs,with the exception of hyaluronan,are produced by extraction from animal tissues.However,limited availability,poor control of animal tissues,impurities,viruses,prions,endotoxins,contamination and other problems have increased the interest in new approaches for GAG production.These new approaches include GAGs production by chemical synthesis,chemoenzymatic synthesis and metabolic engineering.One chemically synthesized heparin pentasaccharide,fondaparinux sodium,is in clinical use.Mostly,hyaluronan today is prepared by microbial fermentation,largely replacing hyaluronan from rooster comb.The recent gram scale chemoenzymatic synthesis of a heparin dodecasaccharide suggests its potential to replace currently used animal-sourced low molecular weight heparin(LMWH).Despite these considerable successes,such high-tech approaches still cannot meet worldwide demands for GAGs.This review gives a brief introduction on the manufacturing of unfractionated and low molecular weight heparins,the chemical synthesis and chemoenzymatic synthesis of GAGs and focuses on the progress in the bioengineered preparation of GAGs,particularly heparin.