Synthesis and Catalytic Properties of 4-Aryl-2,3-dihydro-4H-pyrimido[2,3-b]benzothiazoles for Asymmetric Acyl or Carboxyl Group Transfer Reactions

2011 ◽  
Vol 76 (16) ◽  
pp. 6678-6685 ◽  
Author(s):  
Baby Viswambharan ◽  
Tatsuya Okimura ◽  
Satoko Suzuki ◽  
Sentaro Okamoto
Keyword(s):  
Catalytic Properties ◽  
Transfer Reactions ◽  
Carboxyl Group ◽  
Group Transfer

scholarly journals Catalytic Diversity of GH30 Xylanases

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4528
Author(s):  
Katarína Šuchová ◽  
Vladimír Puchart ◽  
Nikolaj Spodsberg ◽  
Kristian B. R. Mørkeberg Krogh ◽  
Peter Biely
Keyword(s):  
Methyl Ester ◽  
Catalytic Properties ◽  
Specific Activity ◽  
Current Knowledge ◽  
Carboxyl Group ◽  
Weak Effect ◽  
Bacterial Enzymes ◽  
Catalytic Activities ◽  
Almost All ◽  
Free Carboxyl

Catalytic properties of GH30 xylanases belonging to subfamilies 7 and 8 were compared on glucuronoxylan, modified glucuronoxylans, arabinoxylan, rhodymenan, and xylotetraose. Most of the tested bacterial GH30-8 enzymes are specific glucuronoxylanases (EC 3.2.1.136) requiring for action the presence of free carboxyl group of MeGlcA side residues. These enzymes were not active on arabinoxylan, rhodymenan and xylotetraose, and conversion of MeGlcA to its methyl ester or its reduction to MeGlc led to a remarkable drop in their specific activity. However, some GH30-8 members are nonspecific xylanases effectively hydrolyzing all tested substrates. In terms of catalytic activities, the GH30-7 subfamily is much more diverse. In addition to specific glucuronoxylanases, the GH30-7 subfamily contains nonspecific endoxylanases and predominantly exo-acting enzymes. The activity of GH30-7 specific glucuronoxylanases also depend on the presence of the MeGlcA carboxyl, but not so strictly as in bacterial enzymes. The modification of the carboxyl group of glucuronoxylan had only weak effect on the action of predominantly exo-acting enzymes, as well as nonspecific xylanases. Rhodymenan and xylotetraose were the best substrates for exo-acting enzymes, while arabinoxylan represented hardly degradable substrate for almost all tested GH30-7 enzymes. The results expand current knowledge on the catalytic properties of this relatively novel group of xylanases.

Correlation of the solid-state reactivities of racemic 2,4(6)-di-O-benzoyl-myo-inositol 1,3,5-orthoformate and its 4,4′-bipyridine cocrystal with their crystal structures

2014 ◽  
Vol 70 (11) ◽  
pp. 1040-1045 ◽  
Author(s):  
Majid I. Tamboli ◽  
Vir Bahadur ◽  
Rajesh G. Gonnade ◽  
Mysore S. Shashidhar
Keyword(s):  
Solid State ◽  
Self Assembly ◽  
Transfer Reaction ◽  
Acyl Transfer ◽  
Transfer Reactions ◽  
Group Transfer ◽  
Hydrogen Bonding Interactions ◽  
Benzoyl Group ◽  
The Stability ◽  
Group Migration

Racemic 2,4(6)-di-O-benzoyl-myo-inositol 1,3,5-orthoformate, C21H18O8,(1), shows a very efficient intermolecular benzoyl-group migration reaction in its crystals. However, the presence of 4,4′-bipyridine molecules in its cocrystal, C21H18O8·C10H8N2,(1)·BP, inhibits the intermolecular benzoyl-group transfer reaction. In(1), molecules are assembled around the crystallographic twofold screw axis (baxis) to form a helical self-assembly through conventional O—H...O hydrogen-bonding interactions. This helical association places the reactive C6-O-benzoyl group (electrophile, El) and the C4-hydroxy group (nucleophile, Nu) in proximity, with a preorganized El...Nu geometry favourable for the acyl transfer reaction. In the cocrystal(1)·BP, the dibenzoate and bipyridine molecules are arranged alternately through O—H...N interactions. The presence of the bipyridine molecules perturbs the regular helical assembly of the dibenzoate molecules and thus restricts the solid-state reactivity. Hence, unlike the parent dibenzoate crystals, the cocrystals do not exhibit benzoyl-transfer reactions. This approach is useful for increasing the stability of small molecules in the crystalline state and could find application in the design of functional solids.

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