Query: selective peptide synthesis of gly-val

title: 4 Sulfobenzyl ester its use in peptide synthesis
abstract: Amino acid 4 sulfobenzyl esters were employed for the synthesis of peptides in solution. They significantly increase the hydrophilicity of protected intermediates as shown by analytical reversed phase high performance liquid chromatography and counter current distribution. General methods for working up are described which permit simple and standardized isolations of products. The use of several coupling methods was demonstrated in the synthesis of Z Val Gly OBzl SO3NH4. Ion exchange chromatography was introduced as a selective purification procedure for protected peptide 4 sulfobenzyl esters. A step wise synthesis of [Leu5] enkephalin was performed, starting from leucine 4 sulfobenzyl ester. Removal of N terminal protecting groups produced zwitterionic peptide 4 sulfobenzyl esters. These were readily purified by crystallization from slightly acidic media; no further purification was necessary. The biologically fully active pentapeptide Tyr Gly Gly Phe Leu was obtained in an overall yield of 30.2%

title: Design and synthesis of potent, highly selective vasopressin hypotensive agonists
abstract: We report here the solid phase synthesis and vasodepressor potencies of a new lead vasopressin (VP) hypotensive peptide [1(b mercapto b,b pentamethylenepropionic acid) 2 0 ethyl D tyrosine, 3 arginine, 4 valine, 7 lysine, 9 ethylenediamine] lysine vasopressin, d(CH2)5[D Tyr(Et)2, Arg3, Val4, Lys7, Eda9]LVP (C) and 21 analogues of C with single modifications at positions 9 (1 13) 6 (14) 2 (16 20) and combined modifications at positions 6 and 10 (15) and 2 and 10 (21) Peptides 1 13 have the following replacements for the Eda residue at position 9 in C: (1) Gly NH2; (2) Gly NH CH3; (3) Ala NH2; (4) Ala NH CH3, (5) Val NH2; (6) Cha NH2; (7) Thr NH2; (8) Phe NH2; (9) Tyr NH2; (10) Orn NH2; (11) Lys NH2; (12) D Lys NH2; (13) Arg NH2. Peptide 14 has the Cys residue at position 6 replaced by Pen. Peptide 15 is the retro Tyr10 analogue of peptide 14. Peptides 16 20 have the D Tyr(Et) residue at position 2 in C replaced by the following substituents: D Trp (16) D 2 Nal (17) D Tyr(But)(18) D Tyr(Prn) (19) D Tyr(Pri) (20) Peptide 21 is the retro Tyr10 analogue of peptide 20. C and peptides 1 21 were evaluated for agonistic and antagonistic activities in in vivo vasopressor (V1a receptor) antidiuretic (V2 receptor) and in in vitro (no Mg2+ oxytocic (OT receptor) assays in the rat, and, like the original hypotensive peptide, d(CH2)5[D Tyr(Et)2, Arg3, Val4]AVP (A) (Manning et al.  were found to exhibit no or negligible activities in these assays. Vasodepressor potencies were determined in anesthetized male rats with baseline mean arterial blood pressure (BP) maintained at 100 120 mmHg. The effective dose (ED) in ug/100 g i.v. the dose required to produce a vasodepressor response of 5 cm2 area under the vasodepressor response curve (AUC) during the 5 min period following the injection of the test peptide, was determined. The EDs measure the vasodepressor potencies of the hypotensive peptides C and 1 21 relative to that of A (ED 4.66 ug/100 g) and to each other. The following ED values in ug/100 g were obtained for C and for peptides 1 21; C 0.53; (1) 2.41; (2) 1.13; (3) 1.62; (4) 0.80; (5) 1.83; (6) 1.56; (7) 2.12, (8) 2.58; (9) 1.40; (10) 0.88; (11) 0.90; (12) 0.85; (13) 0.68; (14) 0.99; (15) 1.05; (16) 0.66; (17) 0.54; (18) 0.33; (19) 0.18; (20) 0.15; (21) 0.14. All of the hypotensive peptides reported here are more potent than A. Peptides 20 and 21 exhibit a striking 30 fold enhancement in vasodepressor potencies relative to A. With a vasodepressor ED 0.14, peptide 21 is the most potent VP vasodepressor agonist reported to date. Because it contains a retro Tyr10 residue, it is a promising new radioiodinatable ligand for the putative VP vasodilating receptor. Some of these new hypotensive peptides may be of value as research tools for studies on the complex cardiovascular actions of VP and may lead to the development of a new class of antihypertensive agents.

title: An improved synthesis of a selective avb3 integrin antagonist cyclo( RGDfK
abstract: The cyclic pentapeptide cyclo Arg Gly Asp d Phe Lys is a highly potent and selective inhibitor for the a v b 3 integrin. A related compound, cyclo Arg Gly Asp d Phe Val is a promising anticancer drug candidate; it inhibits angiogenesis and induces apoptosis in vascular cells. We have developed an improved solid phase synthesis based on Kessler's procedure to afford cyclo RGDfK peptide in high purity and high yield in a multi gram scale. This improved synthesis is environmentally friendly and may be generally applicable to other related cyclic peptide syntheses.

title: Isolation and synthesis of a host selective toxin produced by Alternaria alternata
abstract: Two phytotoxins are isolated from culture filtrates of an Alternaria alternata pathogenic to sunflower. One was identified by chemical and physicochemical techniques as the tetrapeptide Ser Val Gly Glu. This peptide, for which we suggested the name AS I toxin, was further characterised by synthesis and by its phytotoxic effect on sunflower and other plants.

title: Design and synthesis of a kininogen based selective inhibitor of thrombin induced platelet aggregation.
abstract: Thrombin induced platelet aggregation has been suggested to play an important role in reocclusion following thrombolytic therapy or angioplasty for treatment of myocardial infarction. We previously demonstrated that thrombin induced platelet aggregation is indirectly mediated by intracellularly activated calpain expressed on the platelet surface through the cleavage of aggregin, a putative ADP receptor, and that high molecular weight kininogen (HK) a naturally occurring thiol protease inhibitor, modulates thrombin induced platelet aggregation. Considering the substrate specificity of calpain and the conserved sequence in HK, we studied selective inhibitors of thrombin induced platelet aggregation by the affinity labeling approach with an S 3 nitro 2 pyridinesulfenyl (Npys) group. H Phe Gln Val Val Cys (Npys) Gly NH2, which combines chemical and structural features of calpain substrate specificity and the conserved sequence in HK, selectively inhibited thrombin induced platelet aggregation. It did not inhibit the aggregatory effects of other platelet agonists, and did not inhibit amidolytic activity of thrombin and thrombin induced platelet shape change. The design and synthesis of such inhibitors could lead to the development of a new class of inhibitors that selectively block thrombin induced platelet aggregation.

title: Synthesis and biological evaluation in vitro of selective, high affinity peptide antagonists of human melanin concentrating hormone action at human melanin concentrating hormone receptor 1.
abstract: Human melanin concentrating hormone (hMCH) and many of its analogues are potent but nonspecific ligands for human melanin concentrating hormone receptors 1 and 2 (hMCH 1R and hMCH 2R) To differentiate between the physiological functions of these receptors, selective antagonists are needed. In this study, analogues of Ac Arg(6) cyclo(S S)(Cys(7) Met(8) Leu(9) Gly(10) Arg(11) Val(12) Tyr(13) Arg(14) Pro(15) Cys(16) NH(2) a high affinity but nonselective agonist at hMCH 1R and hMCH 2R, were prepared and tested in binding and functional assays on cells expressing these receptors. In the new analogues, 5 aminovaleric acid (Ava) was incorporated in place of the Leu(9) Gly(10) and/or Arg(14) Pro(15) segments of the disulfide ring. Several of these compounds turned out to be high affinity antagonists selective for hMCH 1R. Moreover, even at micromolar concentrations, they were devoid of agonist potency at both hMCH receptors and not effective as hMCH 2R antagonists. For example, peptide 14, Gva(6) cyclo(S S)(Cys(7) Met(8) Leu(9) Gly(10) Arg(11) Val(12) Tyr(13) Ava(14,15) Cys(16) NH(2) (Gva 5 guanidinovaleric acid) was a full competitive hMCH 1R antagonist (IC(50) 14 nM, K(B) 0.9 nM) with more than 1000 fold selectivity over hMCH 2R. Examination of various compounds with Ava in positions 9,10 and/or 14,15 revealed that the Leu(9) Gly(10) and Arg(14) Pro(15) segments of the disulfide ring are the principal structural elements determining hMCH 1R selectivity and ability to act as a hMCH 1R antagonist.

title: Design and synthesis of conformationally constrained somatostatin analogues with high potency and specificity for mu opioid receptors.
abstract: A series of cyclic, conformationally constrained peptides related to somatostatin were designed and synthesized in an effort to develop highly selective and potent peptides for the mu opioid receptor. The following new peptides were prepared and tested for their mu opioid receptor potency and selectively in rat brain binding assays: D Phe Cys Tyr D Trp Orn Thr Pen Thr NH2 (2, CTOP) D Phe Cys Tyr D Trp Arg Thr Pen Thr NH2 (3, CTAP) D Phe Cys Tyr D Trp Nle Thr Pen Thr NH2 (4) D Phe Cys Tyr D Trp Lys Val Pen Thr NH2 (5) D Phe Cys Tyr D Trp Lys Gly Pen Thr NH2 (6) D Phe Cys Tyr Trp Lys Thr Pen Thr NH2 (7) D Tyr Cys Tyr D Trp Lys Thr Cys Thr OH (8) D PhGly Cys Tyr D Trp Lys Thr Pen Thr NH2 (9) and D PhGly Pen Phe D Trp Lys Thr Cys Thr OH (10) The most selective peptide, 2 (CTOP) displayed both high affinity (IC50 3.5 nM) and exceptional selectivity (IC50 delta/IC50 mu 4,000) for mu opioid receptors. Furthermore, 2 exhibited very low affinity for somatostatin receptors in the rat brain (IC50 greater than 24,000 nM) with an IC50 somatostatin/IC50 mu receptor selectivity of 8,750. These conformationally constrained cyclic peptides should provide new insight into the structural and conformational requirements for the mu opioid receptor and the physiological role of this receptor.

title: Synthesis and biological activities of cyclic lanthionine enkephalin analogues: delta opioid receptor selective ligands.
abstract: The synthesis and biological test results of a series of enkephalin analogues incorporating the lanthionine modification are presented. The syntheses of four monosulfide bridged analogues of enkephalins, Tyr c[D Ala(L) Gly Phe D Ala(L) OH (1a) Tyr c[D Val(L) Gly Phe D Ala(L) OH (1b) Tyr c[D Ala(L) Gly Phe Ala(L) OH (1c) and Tyr c[D Val(L) Gly Phe Ala(L) OH (1d) where Ala(L) and Val(L) denote the lanthionine amino acid ends linked by a monosulfide bridge to form the lanthionine structure, were successfully carried out via preparation of the linear peptide on solid support and cyclization in solution. In vitro binding assays against mu delta and kappa opioid receptors and in vitro tests using GPI and MVD assays revealed that the dimethyl lanthionine analogues 1b and 1d, denoted as D Val(L) in position 2, show substantial selectivity toward the delta opioid receptor, while the unsubstituted analogues 1a and 1c, denoted as D Ala(L) in position 2, bind to both mu and delta opioid receptors. The in vivo thermal escape assay by intrathecal administration showed that the analogues 1b and 1d are among the most potent ligands at producing antinociception through the delta opioid receptor. The picomolar potencies of analogues 1a and 1c in the intrathecal (it. assay strongly indicate that mu and delta opioid receptors interact synergistically to modulate the antinociceptive responses.

title: Selective coupling of methotrexate to peptide hormone carriers through a y carboxamide linkage of its glutamic acid moiety Benzotriazol 1 yloxytris dimethylamino phosphonium hexafluorophosphate activation in salt coupling drg targeting cyttooic peptides slte seectve conJugation chemoth
abstract: A convenient synthetic method is described for the preparation ofpeptide methotrexate (MTX) conjugates in which MTX is coupled selectively through the ycarboxyl group of its glutamic acid moiety to a free amino group in peptide analogs. The syntheses of a somatostatin analog MTX conjugate (MTX D Phe Cys Tyr D Trp Lys Val Cys ThrNH2) (AN 51) and two conjugates of analogs of luteinizing hormone releasing hormone (LH RH) with MTX [Glp HisTrp Ser Tyr D Lys(MTX) Leu Arg Pro Gly NH2I (AJ 04) and [Ac Ser Tyr D Lys(MTX) Leu Arg Pro NH Et] AJ 51 are presented as examples. Benzotriazol 1 yloxyris(dimethylamino)phosphonium hexafluorophosphate (BOP reagent) was used in the synthesis for activation of 4 amino 4 deoxy N1degmethylpteroic acid, which reacted with the potassium salt of glutamic acid a teil butyl ester in dimethyl sulfoxide to form the suitably protected MTX derivative. This synthesis provides an example of the high suitabilit of BOP reagent for the salt coupling method. The selectively protected MTX derivative was then coupled to the different peptide carriers and deprotected under relatively mild conditions by trifluoroacetic acid. The conjugates of MTX with hormonal analogs are suitable for targeting to various tumors that possess receptors for the peptide moieties. Drug targeting is a modem approach aimed at decreasing the undesired side effects ofantineoplastic agents caused by their nonselective action on various human tissues. In view of extensive investigation of analogs of different peptide hormones such as luteinizing hormone releasing hormone (LHRH) somatostatin, and, recently, bombesin (1 3) for the treatment of some cancers, we also endeavored to use them as carrier molecules for different chemotherapeutic agents in cases in which direct action of these peptides on the membrane receptors on tumors could be established (2, 4) Methotrexate (MTX) is a well known and extensively characterized antineoplastic agent chemically suitable for conjugation to peptides. This compound is a potent inhibitor of the enzyme dihydrofolate reductase, which is responsible for recycling 7,8 dihydrofolate to its reduced, physiologically active 6(R) tetrahydro form (5) Although not all types of tumors are affected by MTX, this cytotoxic agent has been used successfully in chemotherapy for more than 4 decades. While searching for more potent analogs of MTX, it was shown that certain alterations can be made within the side chain of its glutamic acid moiety without loss of activity (6) A "bulk tolerance" at the t carboxyl position of its glutamic acid moiety has also been reported (6) This makes MTX The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. SS1734 solely to indicate this fact. suitable for conjugation even to large "carriers" such as peptide hormones. These conjugates can preserve MTX like antifolate activity and then be targeted to tumor cells that have specific receptors for the peptide portion of the hybrid molecule. In this paper, we describe a convenient synthesis of a selectively protected MTX derivative, utilizing benzotriazol1 yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP reagent) in the salt coupling method. The use of the salt coupling method makes it possible to protect one carboxyl group in glutamic acid only by salt formation during acylation by 4 amino 4 deoxy N10 methylpteroic acid (APA) thus simplifying the preparation to a one vessel reaction  This intermediate was used for synthesis ofpeptide MTX conjugates, where MTX was coupled to a free amino group in the peptide carrier through a carboxamide linkage of its glutamic acid moiety. Syntheses of a somatostatin MTX conjugate (AN 51) and two conjugates of LH RH analogs with MTX (AJ 04 and AJ 51) are presented as examples.  The LH RH analogs and the somatostatin analog used as carriers were synthesized in our laboratory as described (7 10) APA was purchased from Aldrich; BOP reagent was purchased from Peptides International (Louisville, KY) Preparation of tert butyl ester of the a carboxyl group of the glutamic acid moiety inMTX (MTX a OtBu) APA hemihydrochloride dihydrate (38 mg; 100 ,umol) was dissolved in 300 A1 of dimethyl sulfoxide (DMSO) in the presence of 21 1d (150 ,umol) of triethylamine (TEA) To this solution 48.6 mg (110 ,mol) of BOP reagent was added. After stirring for 30 min, a yellow precipitate appeared. A solution of22.4 mg (110 ,mol) of Glu a OtBu and 7.6 mg (55 ,umol) of K2CO3 in 300 j4 ofDMSO was then added to the reaction mixture. After 5 min at 50degC, a clear solution was obtained. The reaction, monitored by analytical HPLC, was completed after stirring for 2 hr at room temperature. The product was isolated from DMSO either by evaporation in a SpeedVac centrifuge evaporator or by precipitation with ethyl acetate/diethyl ether (1:1) (vol/vol) This crude material was purified by reversedAbbreviations: APA, 4 amino 4 deoxy N10 methylpteroic acid; BOP reagent, benzotriazol 1 yloxytris(dimethylamino)phosphonium hexafluorophosphate; DMF, N,N dimethylformamide; DMSO, dimethyl sulfoxide; LH RH, luteinizing hormone releasing hormone; MTX, methotrexate; OtBu, tert butyl ester; TEA, triethylamine; TFA, trifluoroacetic acid. tOn leave from Institute for Drug Research, H 1325 Budapest P.O. Box 82, Hungary. SSTo whom reprint requests should be addressed at: Veteran's Affairs Medical Center, 1601 Perdido Street, New Orleans, LA 70146.

title: Selective coupling of methotrexate to peptide hormone carriers through a gamma carboxamide linkage of its glutamic acid moiety: benzotriazol 1 yloxytris(dimethylamino)phosphonium hexafluorophosphate activation in salt coupling.
abstract: A convenient synthetic method is described for the preparation of peptide methotrexate (MTX) conjugates in which MTX is coupled selectively through the gamma carboxyl group of its glutamic acid moiety to a free amino group in peptide analogs. The syntheses of a somatostatin analog MTX conjugate (MTX D Phe Cys Tyr D Trp Lys Val Cys Thr NH2) (AN 51) and two conjugates of analogs of luteinizing hormone releasing hormone (LH RH) with MTX [Glp His Trp Ser Tyr D Lys(MTX) Leu Arg Pro Gly NH2] (AJ 04) and [Ac Ser Tyr D Lys(MTX) Leu Arg Pro NH Et] AJ 51 are presented as examples. Benzotriazol 1 yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP reagent) was used in the synthesis for activation of 4 amino 4 deoxy N10 methylpteroic acid, which reacted with the potassium salt of glutamic acid alpha tert butyl ester in dimethyl sulfoxide to form the suitably protected MTX derivative. This synthesis provides an example of the high suitability of BOP reagent for the salt coupling method. The selectively protected MTX derivative was then coupled to the different peptide carriers and deprotected under relatively mild conditions by trifluoroacetic acid. The conjugates of MTX with hormonal analogs are suitable for targeting to various tumors that possess receptors for the peptide moieties.