| 7188908 |
Amaninamide, a new toxin of Amanita virosa mushrooms |
10.1007/BF02003953. |
Experientia |
Amaninamide, a new toxin of Amanita virosa mushrooms
Abstract
- Amaninamide, a toxin closely related to the family of amatoxins, was found exclusively in Amanita virosa mushrooms. It differs from the well known toxin alpha-amanitin in that it lacks the 6'-hydroxyl group of the tryptophan unit, and from the toxin amanin found in Amanita phalloides by the presence of a carboxamide group instead of a carboxylic acid groups."
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| 7198111 |
New insecticidal cyclodepsipeptides from the fungus Isaria felina. I. Production, isolation and insecticidal properties of isariins B, C and D |
10.7164/antibiotics.34.1261. |
J Antibiot (Tokyo) |
New insecticidal cyclodepsipeptides from the fungus Isaria felina. I. Production, isolation and insecticidal properties of isariins B, C and D
Abstract
- Three new cyclodepsipeptides related to the previously described isariin were isolated from a strain of Isaria felina. They were named isariins B, C and D. Isariin D and, to a lesser extent, isariin C, exhibited insecticidal activity against Galleria mellonella larvae, whereas isariin B and isariin itself proved inactive.
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| 7198112 |
New insecticidal cyclodepsipeptides from the fungus Isaria felina. II. Structure elucidation of isariins B, C and D |
10.7164/antibiotics.34.1266. |
J Antibiot (Tokyo) |
New insecticidal cyclodepsipeptides from the fungus Isaria felina. II. Structure elucidation of isariins B, C and D
Abstract
- Isariins B, C and D, isolated from a strain of Isaria felina, were shown to be cyclodepsipeptides constituted by a pentapeptide cyclized through a beta-hydroxyacid. The nature of the latter and the sequence of the peptide were determined for each compound. Relations between insecticidal activity and structure of the depsipeptides were pointed out.
|
| 7233187 |
Didemnins: antiviral and antitumor depsipeptides from a caribbean tunicate |
10.1126/science.7233187. |
Science |
Didemnins: antiviral and antitumor depsipeptides from a caribbean tunicate
Abstract
- Extracts of samples of a Caribbean tunicate (ascidian, sea squirt) of the family Didemnidae inhibit in vitro at low concentrations the growth of DNA and RNA viruses as well as L1210 leukemic cells. The active compounds isolated from the tunicate, didemnins A, B, and C, are depsipeptides, and didemnin B (a derivative of didemnin A) is the component active at the lowest concentration in inhibiting viral replication in vitro and P388 leukemia in vivo.
|
| 7275003 |
N-(9-Xanthenyl)amino acid N-carboxyanhydrides in the solid-phase synthesis of a Lys-Lys-linked cyclic leucine-enkephalin |
10.1515/bchm2.1981.362.1.593. |
Hoppe Seylers Z Physiol Chem |
N-(9-Xanthenyl)amino acid N-carboxyanhydrides in the solid-phase synthesis of a Lys-Lys-linked cyclic leucine-enkephalin
Abstract
- The side-chain-protected heptapeptide Phe-Leu-Lys(F3Ac)-Lys(F3Ac)-Tyr(Cac)-Gly-Gly is assembled by stepwise chain elongation on a polystyrene resin, using inter alia N-(9-xanthenyl)-amino acid N-carboxyanhydrides. After HBr cleavage from the resin, cyclization via carbodiimide/N-hydroxysuccinimide is carried out in a yield of 24%. Cleavage of the 9-carbazolylcarbonyl group by hydrazinolysis, and alkaline hydrolysis of the trifluoroacetyl groups, affords cyclo (-Tyr-Gly-Gly-Phe-Leu-Lys-Lys-) in an over-all yield of 12%. The structure of the peptides is confirmed by mass spectrometry.
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| 7309348 |
Synthesis of 8-L-tryptophan-oxytocin and determination of one of its conformational parameters |
10.1111/j.1399-3011.1981.tb02013.x. |
Int J Pept Protein Res |
Synthesis of 8-L-tryptophan-oxytocin and determination of one of its conformational parameters
Abstract
- The hormone analog 8-L-tryptophan-oxytocin was synthesized in solution by stepwise chain lengthening from the C-terminal residue. Active esters of 9-fluorenylmethyloxycarbonyl (Fmoc)-amino acids were used for the incorporation of individual residues and thereby exposure to the tryptophan-containing intermediates both to acid conditions and to alkylation could be avoided. In a parallel experiment the parent compound, oxytocin, was prepared similarly. The final products were purified by countercurrent distribution. The presence of tyrosine (donor) and tryptophan (acceptor) in the chain was used for the measurement of the average intramolecular Tyr2-Trp8 distance by evaluation of intramolecular resonance energy transfer between their fluorescent side chains. Since the 8-L-tryptophan analog has high affinity for oxytocin receptors, it is reasonable to assume that its conformation is similar to that of the parent molecule and that in the latter the leucine-tyrosine distance is of about the same length. The distance of 13.5 Ao between the side chains of tyrosine and tryptophan measured in aqueous solution is compatible with the Tyr2-Leu8 distance determined with molecular models built according to the proposals of Walter for the biologically active conformation of oxytocin.
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| 7328064 |
Synthetic studies on gratisin |
10.7164/antibiotics.34.1227. |
J Antibiot (Tokyo) |
Synthetic studies on gratisin
Abstract
|
| 7337939 |
Structure and analgesic activity relationship of cyclo-tyrosyl-arginyl and its three stereoisomers |
10.1248/cpb.29.3403. |
Chem Pharm Bull (Tokyo) |
Structure and analgesic activity relationship of cyclo-tyrosyl-arginyl and its three stereoisomers
Abstract
|
| 7341523 |
Cyclic analogue of bradykinin possessing selective and prolonged biological activity |
10.1111/j.1399-3011.1981.tb02985.x. |
Int J Pept Protein Res |
Cyclic analogue of bradykinin possessing selective and prolonged biological activity
Abstract
- Cyclo-(N epsilon 1-Lys1, Gly6)-bradykinin and its deprotected non-cyclic precursor, PheGlyProPheArg LysProProGly, were synthesized using the conventional methods of peptide chemistry. Similar to bradykinin, the cyclopeptide elicits a depressor reaction in rats, as revealed by the experiments in vivo. Its duration of action, however, is greater by several orders of magnitude. At the same time, it appears to exhibit no myotropic activity when applied in vitro to extravasal smooth muscle preparations (uterus and ileum of the rat). The non-cyclic precursor lacks the depressor activity, but produces a slight myotropic effect (alpha = 0.6 +/- 0.09; pD2 = 5.9 +/- 0.17).
|
| 7341525 |
Cyclic peptides. XI. Synthesis of AM-toxin analogs by intramolecular condensation of pyruvyl-tripeptide amides |
None |
Int J Pept Protein Res |
Cyclic peptides. XI. Synthesis of AM-toxin analogs by intramolecular condensation of pyruvyl-tripeptide amides
Abstract
- In order to establish possible routes for the synthesis of AM-toxins, cyclotetradepsipeptides containing Dha, Pyr-L-Ala-L-Hmb-L-Tyr-NH2 were prepared and treated with TFA or anhydrous HF. The product was identified to be cyclo (-alpha-Hyala-L-Ala-L-Hmb-L-Tyr-), resulting from intramolecular condensation of the alpha-keto and amide group with the formation of the alpha-Hyala residue. Cyclo (-alpha-Hyala-L-Ala-L-Hmb-L-Phe-) and cyclo (-alpha-Hyala-L-Ala-L-Val-L-Phe-) were obtained by acid-treatment of the corresponding pyruvyl-tripeptide amides. The cyclic tetrapeptides did not show the activity of AM-toxin.
|
| 7349976 |
The design of effective in vivo antagonists of rat uterus and milk ejection responses to oxytocin |
10.1210/endo-106-1-81. |
Endocrinology |
The design of effective in vivo antagonists of rat uterus and milk ejection responses to oxytocin
Abstract
- Several new synthetic analogs of the oxytocin antagonist 1-deaminopenicillamineoxytocin have been prepared and tested for their abilities to inhibit responses to oxytocin by the isolated rat uterus in the absence and presence of Mg++, by the rat uterus in situ, and by the rat mammary gland in situ. Substituting 2-O-methyltyrosine in 1-deaminopenicillamineoxytocin strikingly enhances antagonism of all uterin responses, and 1-deaminopenicillamine, 2-O-methyltyrosineoxytocin and its 4-threonine analog are also potent inhibitors of the milk ejection response. Substituting 2-phenylalanine in 1-deaminopenicillamineoxytocin also enhances antagonistic activities in all uterine assays, but 1-deaminopenicillamine, 2-phenylalanineoxytocin retains agonistic activity on milk ejection assays. From these studies we can conclude that changes in the 1-position (1-deaminopenicillamine substitution) and the 2-position (2-O-methyltyrosine or 2-phenylalanine substitution) can have additive effects on antagonistic activities. Substitution of an 8-ornithine also enhances inhibitory potency in vivo, and this effect may also be additive to those of the substitutions in 1- and 2-positions. These findings provide many clues that may lead to the design of even more effective antagonists; several of the analogs reported here appear to the most effective antagonists of oxytocin in vivo yet reported and may be useful agents in further studies on the physiological functions of endogenous oxytocin.
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| 7359343 |
Natriuretic effect of 7-glycineoxytocin in the presence of diuretic agents in conscious rats |
None |
J Pharmacol Exp Ther |
Natriuretic effect of 7-glycineoxytocin in the presence of diuretic agents in conscious rats
Abstract
- Substitution of the amino acid glycine for 7-proline in oxytocin produces an analog, 7-glycineoxygocin, having markedly reduced antidiuretic and vasopressor activities but retaining considerable natriuretic activity. We administered this analog alone and with distally acting diuretic agents to test the hypothesis that oxytocin and its analogs decrease proximal tubular fluid reabsorption. If 7-glycineoxytocin shares a common mechanism of action with any of these agents, the response to combined treatment should be less than additive, otherwise, the saluretic effect of both agents should be maintained. Subcutaneous administration of 7-glycineoxytocin, 10 micrograms/kg, to conscious fluid-loaded rats produced a natriuresis, diuresis and kaliuresis. Hydrochlorothiazide and 7-glycineoxytocin administered together to the same rats had a greater than additive effect on urine volume and sodium excretion. Furosemide and 7-glycineoxytocin had an additive effect on urine volume, sodium and chloride excretion. Triamterene blocked the kaliuresis caused by 7-glycineoxytocin, although the two agents administered together had a greater than additive effect on sodium excretion. These results indicate that 7-glycineoxytocin does not share a common natriuretic mechanism or site of action with the above diuretics. Our data are consistent with the hypothesis that oxytocin and its analogs may increase urinary sodium excretion by decreasing net proximal tubular fluid reabsorption.
|
| 7359538 |
5-(N4,N4-Dimethylasparagine),8-lysinevasopressin: the first 5-position neurohypophyseal hormone analogue to retain to retain significant antidiuretic potency |
10.1021/jm00176a021. |
J Med Chem |
5-(N4,N4-Dimethylasparagine),8-lysinevasopressin: the first 5-position neurohypophyseal hormone analogue to retain to retain significant antidiuretic potency
Abstract
- In the proposed biologically active conformation of vasopressin at the antidiuretic receptor, the side-chain carboxamide group of the 5-position asparaginyl residue has been previously suggested to be the key active element in the hormone for its initiation of the antidiuretic response. 5-(N4,N4-Dimethylasparagine),8-lysinevasopressin, the analogue in which the hydrogen atoms of the -NH2 portion of the primary carboxamide have been replaced by methyl groups, has been synthesized and found to retain about 3% of the antidiuretic potency of lysine-vasopressin (i.e., 5.5 +/- 0.3 units/mg). This result suggests that the hydrogen atoms of the carboxamide moiety are not essential for antidiuretic activity. In addition, the analogue possesses rat pressor, avian vasodepressor, and rat uterotonic potencies of 2.55 +/- 0.05, 0.39 +/- 0.03, and less than 0.05 units/mg, respectively.
|
| 7372403 |
Cyclic peptides. VII. Synthesis and conformation of diastereomeric analogs of cyl-2 containing L-proline and L-leucine |
None |
Int J Pept Protein Res |
Cyclic peptides. VII. Synthesis and conformation of diastereomeric analogs of cyl-2 containing L-proline and L-leucine
Abstract
- Two diastereomeric cyclic tetrapeptides with a sequence of cyclo (-D (and L)-Tyr (me)-L-Ile-L-Pro-L-Leu-) (ID and IL) have been synthesized, which are simplified analogs of a phytotoxic peptide Cyl-2, and contain an L-proline and an L-leucine residue in place of an L-pipecolic acid and a 2-amino-8-oxo-9,10-epoxydecanoic acid residue, respectively, in Cyl-2. The cyclization of the H-D-Tyr(Me)-L-Ile-L-Pro-L-Leu-ONSu proceeded smoothly to give ID in excellent yield (50%), but the cyclization of H-L-Tyr(Me)-L-Ile-L-Pro-L-Leu-ONSu gave IL in much lower yield (10%). Based on the results of 1H- and 13C-n.m.r. studies, differential N-methylation and model buildings of ID, the backbone structure of ID has been proposed to be a unique trans-trans-cis-trans conformation, the L-Ile-L-Pro bond being cis.
|
| 7378373 |
Cyclo(L-prolylglycyl)3 and its sodium, potassium, and calcium ion complexes: a Raman spectroscopic study |
10.1021/bi00550a012. |
Biochemistry |
Cyclo(L-prolylglycyl)3 and its sodium, potassium, and calcium ion complexes: a Raman spectroscopic study
Abstract
- Raman spectra of the cyclic hexapeptide cyclo-(L-prolylglycyl)3 and its Na+, K+, and Ca2+ complexes are reported for the solid state and for samples in solution. Model compounds and N-deuteration were used to aid mode identification. Spectra of the uncomplexed ionophore in solution are consistent with previously proposed solution conformations and permit the identification of spectral lines characteristic of proline-containing peptide bonds in the trans and the cis conformations. Upon cation complexation the prolyl carbonyl stretch bands sharpen and upshift 20-30 cm-1 (to 1690-1700 cm-1). The glycyl carbonyl stretch band is unaffected by Na+ complexation, upshifted approximately 15 cm-1 by K+ complexation, and downshifted approximately 20 cm-1 (to 1619 cm-1) by Ca2+ complexation. Arguments supporting the involvement of prolyl carbonyl groups in cation complexation are noted. Spectra of the Na+ complex of the tetramer cyclo(L-prolylglycyl)4 suggest an asymmetric structure.
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