V. S. Parmar

Regioselective deacylation of polyacetoxy aryl-methyl ketones by lipases in organic solvents☆

Abstract Lipases from porcine pancreas and Candida cylindraea, suspended in organic solvents have been used to study regioselective deacylation of polyacetoxy acetophenones. It has been observed that the hydrolysis of acetate groups at positions other than ortho predominates.

Regioselective esterification of diols and triols with lipases in organic solvents

Abstract Lipases from porcine pancreas (PPL) and Candida cylindracea (CCL) in different organic solvents allow discrimination of the primary and secondary hydroxyl groups, and also between two primary hydroxyl groups towards acylation with 2,2,2-trifluoroethyl butyrate in diols and triols with high regioselectivity.

Isethionate in certain red algae

Isethionic acid (2-hydroxyethanesulfonic acid) was isolated as salts from a methanolic extract ofHypnea musciformis collected in the Indian Ocean and identified by comparison (nuclear magnetic resonance, infrared and mass spectrometry) with an authentic sample. The compound has not previously been reported from plants. Investigations of 13 other species of red algae showed that only some samples of species of the families Gigartinaceae, Hypnaceae and Solieriaceae (all of order Gigartinales) contained isethionates.

Potential applications of enzyme-mediated transesterifications in the synthesis of bioactive compounds

The yeast lipase Candida cylindracea (CCL) and porcine pancreatic lipase (PPL) have been used for regioselective deacylation of peracetylated benzopyrones, diphenylpropenones and acetophenones for the first time. The deacylation study on different classes of polyphenols has revealed that the presence of carbonyl group attached to the aromatic ring is needed by the lipases to exhibit regioselectivity towards hydrolysis of acetoxyl groups. The acetoxyl groups at positions other than the one at ortho position to the carbonyl group get selectively hydrolysed by PPL in orgnnic solvents. The trnnsesterification reactions using triflouroethylbutyrate (TFEB), catalysed by PPL and CCL on some polyols in dry organic solvents were also performed. It was found that the primary hydroxyl is acylated. In D-panthenol, the oxidised dextrorotatory form of which is a major constituent of vitamin B-complex, the primary hydroxyl group at the far end of the asymmetric carbon atom gets exclusively acylated. This work should be of importance in the synthesis of building blocks of biologically active natural products which may provide structural leads to anti AIDS and anticancer agents.

1-(3,4-Dimethoxyphenyl)-3-(3-methylphenyl)prop-2-en-1-one

The synthesis and structure of the title compound, C18H18O3, are described. The molecule is almost flat and the ortho methoxy groups point away from each other.

Prevention of benzene-induced genotoxicity in bone marrow and lung cells: superiority of polyphenolic acetates to polyphenols.

Previous investigations carried out in our laboratory have highlighted that 7,8-diacetoxy-4-methylcoumarin demonstrates a mechanism-based inhibition of cytochrome P450 (Cyt-P450) activities such as microsome-mediated aflatoxin B1 (AFB1) epoxidation, dealkylation of alkylated resorufin, and toxicokinetics of benzene. 7,8-Diacetoxy-4-methylcoumarin, quercetin pentaacetate, and ellagic acid peracetate were also found to be effective in giving the protection of AFB1-induced genotoxicity in rat’s bone marrow and lung cells possibly due to acetylation of Cyt-P450 apoprotein mediated by acetoxy drug: protein transacetylase. Later, this transacetylase was identified as calreticulin, and the acetyltransferase function of calreticulin was appropriately termed calreticulin transacetylase. In this communication, we have focused on the superiority of several classes of polyphenolic acetates to polyphenols in the modification of Cyt-P450-linked mixed function oxidases (MFOs) such as 7-ethoxyresorufin O-deethylase (EROD) and pentoxyresorufin O-dealkylase (PROD). Special attention has also been focused on benzene-induced genotoxicity in bone marrow and lung cells. Results clearly indicated that polyphenolic acetates demonstrated time-dependent inhibition of Cyt-P450-linked MFOs, while parent polyphenols failed to demonstrate the same. Polyphenolic acetates were found to be more superior to polyphenols in preventing benzene-induced micronuclei formation. The pattern of inhibition of Cyt-P450-dependent MFOs and benzene-induced micronuclei formation by polyphenolic acetates was found in tune with their specificities to calreticulin transacetylase. These results further substantiated that inhibition of Cyt-P450-linked MFOs and benzene-induced genotoxicity in bone marrow and lung cells by polyphenolic acetates are mediated by the action of calreticulin transacetylase that catalyzes the acetylation of concerned proteins.

3-Cyano-5-(4-methoxybenzyl)-6-(4-methoxyphenyl)-4-methylthio-2H-pyran-2-one

The synthesis of the title compound, C 22 H 19 NO 4 S, is described. The methyl group of the methylthio substituent points towards the CN group, as has been noted before when bulky substituents occupy the 5-position. The phenyl groups in the 5- and 6-positions are twisted at angles of 75.7 (1) and 36.5 (1)°, respectively, from the plane of the pyrone ring.

6-Hydroxy-5,7-dimethoxy-4-methylcoumarin

The synthesis and structure of the title compound, C 12 H 12 O 5 , are described. The molecule is approximately flat with the exception of the 5-methoxy group which is twisted at 70.1 (3)° with respect to the aromatic ring. The molecules pack together with intermolecular hydrogen bonding between the 04 and 02(x, y, z - 1) atoms.

Synthesis of some new phenyl 2H-1-benzopyran-2-ones: novel structure for nivegin

Abstract The constitution of nivegin, occurring in Echinops niveus has been revised by synthesising 5,7-dihydroxy-4-(4-hydroxyphenyl)-2H-1-benzopyran-2-one(1), 5,7-dihydroxy-3-(4-hydroxyphenyl)-2H-1-benzopyran-2-one(2) and their derivatives 3 - 6. It has been assigned a novel structure having the phenyl substituent in the benzenoid ring of the coumarin nucleus - 4,5-dihydroxy-7-(4-hydroxyphenyl)-2H-1-benzopyran-2-one(11).

1-(3,4-Dimethoxy-α,β-dihydrocinnamoyl)pyrrole, a Novel Amide from Piper brachystachyum

The isolation and structure of the title compound, C 15 H 17 NO 3 , are described. The molecule is twisted so that the two ring systems are oriented at an angle of 64.2 (1)° with respect to one another, and the ortho-methoxy groups, while being almost coplanar with the phenyl ring, point away from each other.