Une nouvelle synthèse de l'oxytocine

Detection of Thiol Functionality and Disulfide Bond Formation by Polyoxometalate

The detection of thiol functionality and intramolecular disulfide bond formation of peptides using the α-Keggin type polyoxometalate molybdenum-oxygen cluster (H₃PMo₁₂O₄₀·nH₂O) is described. Our method entails the addition of this polyoxometalate to solutions of thiol, whereupon the color of the solution changes from colorless to deep blue. Reduction of the polyoxometalate from Mo(VI) to Mo(V) occurs with concomitant oxidation of the thiol functionality, to form disulfide bonds. To exemplify the utility this phenomenon, we accomplished the oxidation of glutathione, reduced linear oxytocin, bactenecin, and α-conotoxin SI; all of which proceeded smoothly and in good conversion in 24 h to less and were accomplished by a change in the color of the reaction solutions.

Synthetic oxytocin and hastening labor: reflections on the synthesis and early use of oxytocin in Brazilian obstetrics

This article reflects on the medicalization of childbirth, focusing on the development of synthetic oxytocin in 1953. Specifically addressed is the social life of oxytocin; in other words, its synthesis, stabilization, and use in obstetrics to hasten labor. Two Brazilian obstetrics journals of this era were surveyed to analyze the early use of synthetic oxytocin in Brazil in the late 1950s, along with obstetric arguments for or against its use. Notable in this period is the increasingly central role of the obstetrician in childbirth, as well as the recommendation to use different interventions linked together (particularly oxytocin) to shorten labor.

Synthesis and biological activity of new potential agonists for the human adenosine A2A receptor

New adenosine derivatives have been synthesized and tested as putative agonists of adenosine receptors. Compounds 2-6 derive from the introduction of several types of substituents (electron donating, electron withdrawing, and halogens) in the para-position of the phenyl ring of the parent compound 1, and compound 7 lacks the hydroxyl group of amino alcohol 1. In radioligand binding assays using recombinant human A(1), A(2A), A(2B), and A(3) receptors, all compounds showed very low or negligible affinity for A(1) and A(2B) receptors but compounds 3, 5, and 7 displayed a remarkably potent affinity for the A(2A) receptor with K(i) values of 1-5 nM. Bromo derivative 3 displayed a selectivity A(1)/A(2A) = 62 and A(3)/A(2A) = 16 whereas the presence of a hydroxyl group (compound 5) improved the selectivity of A(1)/A(2A) and A(3)/A(2A) to 120- and 28-fold, respectively. When the methoxy derivative 4 lacks the hydroxyl group on the side chain (compound 7), the binding affinity for A(2A) is increased to 1 nM, improving selectivity ratios to 356- and 100-fold against A(1) and A(3), respectively. In Chinese hamster ovary cells transfected with human A(2A) and A(2B) receptors, most compounds showed a remarkable activity for the A(2A) receptor, except chloro derivative 2, with EC(50) values ranging from 1.4 to 8.8 nM. The compounds behaved as good A(2A) agonists, and all were more selective than 5'-(N-ethylcarboxamino)adenosine (NECA), with A(2B)/A(2A) ratios of cAMP accumulation ranging from 48 for compound 2 to 666 for compound 7 while the corresponding A(2B)/A(2A) ratio for NECA was only 9. Compounds 1, 3, 5, and 7 also displayed higher selectivities than NECA up to 100-fold in isolated aortas of rat and guinea pig. In guinea pig tracheal rings precontracted by carbachol, compounds 2 and 4 were more potent than adenosine (100-fold) and NECA (10-fold), whereas compounds 1 and 7 displayed similar effects to NECA. Pretreatment of the tracheal rings with A(2), A(2A), and A(2B) receptor antagonists 3,7-dimethyl-l-propargylxanthine, 8-(3-chlorostyryl)caffeine, and alloxazine produced a marked inhibition of the tracheal relaxations induced by compounds 1, 2, and 4, but none of the compounds showed selectivity toward any of the adenosine receptors.

The biological activity of a new analogue of oxytocin in which the tyrosyl group is replaced by phenylalanyl

A new synthetic analogue of oxytocin with a phenylalanyl group instead of a tyrosyl group has been investigated. The most prominent biological properties of this peptide were its oxytocic activity on the rat or cat uterus in vivo and on milk-ejection pressure in the rabbit. Another remarkable feature was the striking difference in pressor activity measured in spinal cats and in anaesthetized rats. The presence of the phenylalanyl group in the molecule in the above-mentioned position did not increase the antidiuretic potency in unanaesthetized rats. The authors propose a nomenclature for the peptides related to oxytocin and vasopressin.

Quinazoline antifolate thymidylate synthase inhibitors: gamma-linked L-D, D-D, and D-L dipeptide analogues of 2-desamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583)

The syntheses of gamma-linked L-D, D-D, and D-L dipeptide analogues of 2-desamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583) are described. The general methodology for the synthesis of these molecules involved the preparation of the dipeptide derivatives employing solution phase peptide synthesis followed by condensation of the dipeptide free bases with the appropriate pteroic acid analogue via diethyl cyanophosphoridate (DEPC) activation. In the final step, tert-butyl esters were removed by trifluoroacetic acid (TFA) hydrolysis. Z-L-Glu-OBut-gamma-D-Ala-OBut, for example, was prepared from alpha-tert-butyl N-(benzyloxycarbonyl)-L-glutamate and tert-butyl D-alaninate via isobutyl-mixed anhydride coupling. The Z-group was removed by catalytic hydrogenolysis and the resulting dipeptide free base condensed with 2-desamino-2-methyl-N10-propargyl-5,8-dideazapteroic acid via DEPC coupling. Finally, tert-butyl esters were removed by TFA hydrolysis to give ICI 198583-gamma-D-Ala. The compounds were tested as inhibitors of thymidylate synthase and L1210 cell growth. Good enzyme and growth inhibitory activity were found with gamma-linked L-D dipeptides, the best examples being the Glu-gamma-D-Glu derivative 35 (Ki = 0.19 nM, L1210 IC50 = 0.20 +/- 0.017 microM) and the Glu-gamma-D-alpha-aminoadipate derivative 39 (Ki = 0.12 nM, L1210 IC50 = 0.13 +/- 0.063 microM). In addition, ICI 198583 L-gamma-D-linked dipeptides were resistant to enzymatic degradation in mice.