ABSTRACT
italic>O-methyltransferases (OMTs) are one of the key tailoring enzymes in the biosynthesis of many natural products, O-methylation can not only reduce the reactivity of natural products, but also alter their solubility, stability and biological activities. Based on the transcriptome data of Ardisia japonica, a full-length cDNA sequence of candidate OMT (termed as AjOMT1) was cloned by reverse transcription-polymerase chain reaction (RT-PCR) and expressed in Escherichia coli (E. coli) for the first time. In vitro enzyme catalytic activity assay showed that the recombinant AjOMT1 could effectively catalyze quercetin to form O-methylated products. Most importantly, AjOMT1 showed unprecedented substrate promiscuity towards structurally various compounds including flavonoids, stilbenes, coumarins, alkaloids and phenylpropanoids, especially preferring to the compounds with adjacent phenolic hydroxyl groups, and showed regio-selectivity. These results suggested that AjOMT1 could be used as the tool enzyme to conduct O-methylation of different types of compounds to produce diverse active methylated products, and provide a new method for drug discovery, even universal part for synthetic biology of natural products.
ABSTRACT
This review aims to focus and highlight the regio-orientation and regioselectivity of the reactions of 3(5)-aminopyrazoleswith 1,3-bielectrophilic reagents that lead to the formation of pyrazolo[1,5-a]pyrimidines. To clarify the significance ofregio-orientation, reactions of 3(5)-aminopyrazoles with symmetric 1,3-bielectrophilic reagents such as acetylacetoneand malononitrile are also included. The comparable nucleophilicity of the exocyclic NH2 group and endocyclicNH in 3(5)-aminopyrazoles is considered as it causes literature controversy associated with regio-orientation of thesubstituents on the pyrimidine ring of pyrazolo[1,5-a]pyrimidine when unsymmetrical 1,3-bielectrophilic reagentreacts with 3(5)-aminopyrazole. To the best of our knowledge, this review would be the first collective and confinedreport to the regio-orientation of pyrazolo[1,5-a]pyrimidines.
ABSTRACT
Se ensayaron algunos fenoles como nucleófilos en la reacción tipo Mannich en medio básico frente al aminal macrocíclico 1,3,6,8-tetrazatriciclo [4.4.1.1(3,8)] dodecano (TATD). Dependiendo del grado de sustitución del fenol empleado, se obtuvieron: 1,3- bis- [2’- hidroxibencil] imidazolidinas regioselectivamente, 2,6-di[3’- (2’’-hidroxibencil)-1’-metilenimidazolidin]fenoles y 3,3’-etilen-bis-(3,4-dihidro-2H-1,3-benzoxazinas).
Several phenols were tested as nucleophilesin Mannich-type reactions with the macrocyclic aminal 1,3,6,8-tetraazatricyclo[4.4.1.1(3,8)]dodecane (TATD) in basic medium. Depending on the degree of substitution of the phenol employed,1,3-bis-[2’-hydroxybenzyl]imidazolidines, 2,6-di[3’-(2’’-hydroxybenzyl)-1’- methyleneimidazolidin] phenols and 3,3’-ethylene-bis-(3,4-dihydro-2H-1,3- benzoxazines) were obtained.