work in the synthesis of podand molecules6), the present paper describes the preparation of certain podand-type trimers of cephalosporin antibiotics (Scheme 1 ). As the central block of the target trimers the tricarboxylic acid 3 was employed, which was obtained by the alkylation of phloroglucinol (1) with methyl bromoacetate and subsequent alkaline hydrolysis. The tert-butyl esters of 7-aminoc...

Magnetic circular dichroism is a suitable technique for semiquantitative determination of total porphyrins in urine and feces, being rapid, reliable, and involving little sample preparation. The sensitivity of the assay suffices to distinguish normal from above-normal concentrations of total porphyrins in urine and feces. Results for urine compare well with those obtained by thin-layer chromato...

Various derivatives of vitamin A, especially esters and ethers , have been studied by many investigators. However, its macromolecular derivatives have scarcely been reported. An attempt was made by the authors to synthesize the macromo lecular derivatives of vitamin A by preparation of the polymerizable derivatives , followed by their polymerization . Thus vitamin A acrylate, methacrylate, crot...

The synthesis of human growth hormone-releasing hormone (hGH-RH), by the chemoselective serine/threonine ligations (STLs) of three unprotected peptide fragments, is reported. To allow for the multiple-fragment ligation, we chose the Msz (p-(methylsulfinyl)benzyloxycarbonyl) group, which is compatible with the preparation of peptide salicylaldehyde esters via Fmoc-SPPS and readily removed by red...

Automating fatty acid derivatization and preparation of calibration standards on an Agilent 7696A Sample Prep WorkBench for fatty acid methyl esters (FAME) analysis can provide comparable precision, better recoveries, and more accurate calibration compared to manual procedures. Hands-on time, reagent usage, and exposure to hazardous chemicals are all greatly reduced. This automated approach has...

A novel migratory dynamic kinetic resolution based on the interplay between an enzyme acylation catalyst and a heterogeneous Brønsted acid as an isomerization/racemization catalyst gives rise to carbocyclic allylic esters with excellent stereoselectivity from readily available tertiary carbinols. An easy-to-use teabag setup combining resin-bound catalysts, a biphasic isooctane-water solvent sys...

We partly purified R-factor-encoded chloramphenicol acetyltransferase (EC 2.3.1.28) from a highly choloramphenicol-resistant mutant derived from Escherichia coli W677/R5. The preparation permitted rapid quanitation of chloramphenicol by use of [14C]acetylcoenzyme A, removing the diacetylated product by selective adsorption onto micropore filters. Succinyl and glucuronyl 3-hydroxyl esters of chl...

In the course of synthesizing a number of aryl phosphate esters as substrates for prostatic acid phosphatase, polymeric phosphorylated products obtained by reaction of 4,4’-dihydroxybiphenyl with phosphorus oxychloride were found to be potent enzyme inhibitors. This report describes the preparation of these anionic polymers and some characteristics of their inhibition of prostatic acid phosphat...

A new tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity...

The first highly enantioselective iridium-catalyzed allylic alkylation that provides access to products bearing an allylic all-carbon quaternary stereogenic center has been developed. The reaction utilizes a masked acyl cyanide (MAC) reagent, which enables the one-pot preparation of α-quaternary carboxylic acids, esters, and amides with a high degree of enantioselectivity. The utility of these ...