During our studies toward the synthesis of ABC ring system hexacyclinic acid, we observed an unexpected influence steric bulk ester group Michael acceptor in a key conjugate addition. We propose eight-membered transition state to explain formation undesired diastereomer case unhindered esters.

Myeloid leukemia cell line HL-60 contains fluoride-sensitive, myeloid-associated isoenzymes of nonspecific esterase that increase in activity when cultures are treated with phorbol ester. These isoenzymes are not detectable in B-lymphoblast cell line KLM-2, either in control or in phorbol-ester-treated cultures. No increased de novo synthesis of the isoenzymes is detectable in HL-60 treated wit...

The liver is capable of storing large quantities of vitamin A in ester form (1). However, some uncertainty still exists concerning both the composition of liver vit,amin A ester and the ability of the liver to esterify vitamin A. Vitamin A palmitate was isolated from fish liver many years ago (a), and recently it has been suggested that this ester is the principal if not exclusive (3, 4) ester ...

The synthesis of 1-(4-boronobenzyl)- 1H-pyrrole was investigated using three different routes. Two key routes that involved the introduction boronate group protected as pinacol ester, failed, due to deprotection problems. route involving final step reaction yielded (10).

N-Benzyloxycarbonyl derivatives of isoglutamine and isoasparagine were coupled with arginine methyl ester through the action of dicyclohexylcarbodiimide. The resulting benzyloxycarbonyl derivatives of isoglutaminylarginine methyl ester and isoasparaginylarginine methyl ester were treated with trypsin for removal of the ester groups and then with porcine pancreatic carboxypeptidase B for liberat...

Regioselective synthesis of cellulose esters is extremely difficult due to the small reactivity differences between cellulose hydroxyl groups, small differences in steric demand between acyl moieties of interest, and the difficulty of attaching and detaching many protecting groups in the presence of cellulose ester moieties without removing the ester groups. Yet the synthesis of homopolymers of...

Synthesis of isoamyl acetate, a flavour ester extensively used in food industry, has been carried out in a solvent-free system. In the present study, an attempt has been made to enhance the isoamyl acetate synthesis yield by transesterification of isoamyl alcohol with vinyl acetate using immobilized Rhizopus oryzae NRRL 3562 lipase. In the present synthesis, substrates had no inhibitory effect ...

Control of boronic acid solution speciation is presented as a new strategy for the chemoselective synthesis of boronic esters. Manipulation of the solution equilibria within a cross-coupling milieu enables the formal homologation of aryl and alkenyl boronic acid pinacol esters. The generation of a new, reactive boronic ester in the presence of an active palladium catalyst also facilitates strea...

A new protocol was developed for the synthesis of sterically demanding imidazolinium salts. This procedure was adopted for the synthesis of seven NHC salts, including ones that were demonstrated to be inaccessible using the conventional orthoformate ester type cyclization method.

Objective(s): This study was performed to investigate the effects of mucosal acidification on mRNA expression and protein synthesis of cystathionine gamma lyase (CSE), cystathionine beta synthase (CBS), and mucosal release of H2S in gastric mucosa in rats. Materials and Methods:Thirty-two rats were randomly assigned into 4 groups (8 in each), including: the control group, HCl (10 mM) treated g...