Novel dual-enzyme system for synthesis of 2-alkyl and 2-arylbenzoxazoles via aerobic oxidation

Abstract

This study reports a strategy involving biocatalysis to form 2-alkylbenzoxazoles and 2-arylbenzoxazoles specifically via the urease-artificial Vitreoscilla hemoglobin metalloenzyme (ArVHbM)-catalyzed cascade reaction of urea, catechols, and aldehydes. In this system,...

Directed evolution of Escherichia coli surface-displayed Vitreoscilla hemoglobin as an artificial metalloenzyme for the synthesis of 5-imino-1,2,4-thiadiazoles

“…Apart from VHb, several hemeproteins and ArMs that were reported in our previous works were also evaluated (Table 1). 34,35 The synthesis of 3aa could not proceed without a catalyst, as shown in entry 1. Cytochrome C, myoglobin, and horseradish peroxidase exhibited low reactivity, while hemoglobins catalyzed the formation of 3aa with better yields (entries 2–10).…”

“…On the basis of the previous literature 10,53,54 and our earlier study on VHb Co -catalyzed aerobic oxidation, 34,35 the mechanism of this reaction was proposed as shown in Scheme 2 . First, amidines (1) and isothiocyanates (2) were coupled spontaneously to generate thiourea intermediate 4.…”

“…27–33 Our group previously reported a Co(ppIX)-linked ArM that was designed based on Vitreoscilla hemoglobin (VHb). 34,35 The cobalt porphyrin cofactor was incorporated into the cavity of VHb (VHb Co ) in vivo by using a porphyrin synthesis-deficient Escherichia coli strain RP523, 36 and a range of engineered VHb Co variants were found to catalyze intramolecular oxidative cyclization for the synthesis of 2-substituted benzoxazoles/benzothiazoles.…”

“…To circumvent the limitation of the directed evolution of VHb Co based on our previous studies, 34,35,46,47 we developed a new approach that uses E. coli surface-displayed method. We created a platform to display VHb Co on E. coli 's outer membrane (VHb SD-Co ) and established a whole-cell high-throughput screening strategy based on ultraviolet (UV) absorption for the in vivo directed evolution of VHb SD-Co with high catalytic reactivity for the synthesis of 5-imino-1,2,4-thiadiazoles.…”

Efficient stereoselective synthesis of aryl lactones using engineered ketoreductase ChKRED20 from Chryseobacterium sp. CA49

“…Biocatalytic approaches have become an important supplementary method for traditional organic synthesis to achieve chiral compounds for their high efficiency, selectivity and environmental friendliness. 5 Currently, biocatalytic syntheses of chiral lactones could be achieved by hydrolase-catalyzed resolutions (KRs or DKRs) of racemic lactone, 6 Baeyer–Villiger monooxygenase (BVMO)-catalyzed oxidation of cyclic ketones, 7 unspecific peroxygenase (UPO)- or cytochrome P450 (CYP)-catalyzed hydroxylation and so on (Fig. 1b).…”