Search PubMed⌕ Search

Biomedical subjects

H Aoyagi

Publications and source records attributed to H Aoyagi.

At least 109 records · Page 6Linked to original sources
PubMed1983

Cyclic peptides. XIII. Asymmetric synthesis of aromatic L-alpha-amino acids through hydrogenation of cyclic dehydrodipeptides.

Four cyclic dehydrodipeptides, cyclo (-delta aminoacyl-L-Ala-), in which aminoacyl is Phe, Apb (2-amino-4-phenylbutanoic acid), App (2-amino-5-phenylpentanoic acid) and Aph (2-amino-6-phenylhexanoic acid), were prepared by condensation of cyclo (-N-Ac-Gly-N-Ac-L-Ala-) with the corresponding aldehydes. Among them, the yield of cyclo (-delta Apb-L-Ala-) was exceptionally low. Each compound was hydrogenated in the presence of Pd black at various temperatures and chiral induction in hydrogenation was evaluated. Low chiral induction at high temperature (50 degrees) was observed in the case of cyclo (-delta Phe-L-Ala-). Optically pure L-Apb, L-App and L-Aph were obtained from the corresponding cyclic dehydrodipeptides, respectively, by hydrogenation and subsequent acid hydrolysis.

Amino Acids↗
PubMed1982

Cyclic peptides. XIV. Syntheses of [4-l-leucine]-, [4-D-leucine]-, and [3-L-proline, 4-D-leucine]-Cyl-2.

Cyl-2 is a phytotoxic cyclic tetrapeptide with the sequence of cyclo(D-Tyr(Me)-L-Ile-L-Pip-Aoe-): Aoe, 2-amino-8-oxo-9,10-epoxydecanoic acid. The configuration of Aoe is unknown. Three analogs, cyclo(-D-Try(Me)-L-Ile-L-Pip-L(and D)-Leu-) (1 and 2) and cyclo(-D-Tyr(Me)-L-Ile-L-Pro-D-Leu-) (3), were synthesized and spectroscopic features of these analogs were compared. 1H-N.m.r. spectra of cyclo(D-Tyr(Me)-L-Ile-L-Pip-L-Leu) (1), cyclo(-D-Tyr(Me)-L-Ile-L-Pro-L-Leu-) (4), and Cyl-2 showed a similar pattern. On the other hand, the spectra of analogs 2 and 3 showed a different pattern, the Ile-Pro bond in 3 being in cis conformation.

Indicators and Reagents↗
PubMed1982

[Etiological studies of manometric asymmetry in the lower esophageal sphincter (LES)].

In order to study the reason for manometric asymmetry of LES, the manometric profile of LES was measured at 3 different points (at the same level) of 20 normal infants and children by using 5 kinds of 3-lumen tubes with different rigidities. The results were; (1) the pressure was highest at 8 degrees (posterolateral wall) in LES by using all of the 5 esophageal tubes (p less than 0.001), and the length was shortest at 8 degrees in LES with 4 esophageal tubes, except for one 8 Fr. silicone tube. With this tube, LES had no asymmetry in the length. (2) The lower the rigidity of the esophageal tube, the less the asymmetry of the LES. In exact terms, the average coefficient of variations of LES pressure and length were; (in order of rigidity) 28.9% and 24.2% with a 12 Fr. vinyl-chloride tube, 25.7% and 23.4% with a 10 Fr. vinyl-chloride tube, 27.2% and 23.6% with a 8 Fr. evatate tube, 24.5% and 22.0% with a 8 Fr. vinyl-chloride tube, and 12.0% and 7.0% with a 8 Fr. silicone tube respectively. The variation in asymmetry of LES pressure and length were smollest by using the latter tube with the lowest rigidity. Therefore, the results suggest that the asymmetrical profile of LES was caused mainly by the rigidity of the esophageal tube rather than by the anatomical specialty of the esophago-cardiac junction.

Child, Preschool↗
PubMed1981

Cyclic peptides. X. Bitter taste and chymotryptic hydrolysis of cyclic depsidipeptides containing a tryptophan residue.

Four stereoisomers (I-LL, I-LD, I-DL and I-DD) of a cyclic depsidipeptide (I) containing a tryptophan and a 2-hydroxy-4-methylpentanoic acid residue were synthesized, and their taste and chymotryptic susceptibility were examined. Compound I-LL is a depsipeptide analog of a bitter principle BP-II, cyclo(-L-Trp-L-Leu-), obtained from casein hydrolyzate. All of the four stereoisomers of I are strongly bitter to taste. Another depsipeptide analog, L-aspartyl-L-2-hydroxy-3-phenylpropanoic acid methyl ester, of the sweet H-L-Asp-L-Phe-OMe showed bitter taste instead of sweet. Chymotrypsin hydrolyzed I-LL and I-LD in moderate rates, and I-DL and I-DD very slowly.

Chymotrypsin↗
PubMed1980

Cyclic peptides. VIII. Synthesis and tryptic hydrolysis of cyclic depsidipeptides containing a lysine residue.

Four stereoisomers of a cyclic depsidipeptide containing a lysine and a 2-hydroxy-3-phenylpropanoic acid (Hpp) residue have been synthesized and their susceptibility toward trypsin examined. Trypsin hydrolyzed cyclo(-L-Lys-L-Hpp-) (I-LL) and cyclo(-L-Lys-D-Hpp-) (I-LD) rapidly and cyclo(-D-Lys-L-Hpp-) (I-DL) and cyclo(-D-Lys-D-Hpp-) (I-DD) very slowly. Proteolytic coefficients of these substrates and a reference compound are shown as follows: I-LL, 112; I-LD, 34; I-DL, 0.34; I-DD, 0.11, and Ac-L-Lys-OEt, 44. Possible mode of actin of trypsin on these substrates was discussed.

Amino Acid Sequence↗
PubMed1980

Cyclic peptides. VII. Synthesis and conformation of diastereomeric analogs of cyl-2 containing L-proline and L-leucine.

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.

Amino Acid Sequence↗
PubMed1980

Cyclic peptides. IX. Asymmetric hydrogenation of alpha, beta-dehydroamino acid residue in cyclodipeptides and preparation of optically pure alpha-amino acids.

A number of cyclo (delta aminoacyl-L-aminoacyl) (delta aminoacyl = delta Aba, delta Val, delta Leu, delta App, delta Phe and delta Trp; L-aminoacyl=L-Ala, L-Val, L-Leu and L-Lys (epsilon-Ac)) were synthesized by the condensation of cyclo (N-acetyl-Gly-N-acetyl-L-aminoacyl) with corresponding aldehyde or acetone and subsequent treatment with hydrazine. Each cyclo (delta aminoacyl-L-aminoacyl) except ones containing delta Phe and delta Trp was hydrogenated using Pd black in methanol to give cyclo (L-aminoacyl-L-aminoacyl) with high chiral induction. In the case of dehydro-cyclodipeptides containing delta Phe or delta Trp, slightly lower chiral induction was observed. Then, a mechanism of asymmetric hydrogenation was proposed. The influence of variation of solvent, temperature and catalyst on asymmetric hydrogenation was examined. Optically pure L-2-aminobutanoic acid, L-2-amino-5-phenylpentanoic acid and L-phenylalanine were synthesized on a preparative scale by this method and subsequent acid-hydrolysis.

Acetone↗
PubMed1979

Cyclic peptides. VI. Asymmetric hydrogenation of dehydroalanine or dehydroaminobutanoic acid residue in cyclodipeptides.

Several cyclo(-L-aminoacyl-deltaAla-) (aminoacyl = Ala, Val, Leu, Phe, Pro and Lys (epsilon-Ac)) were prepared by tosylation and successive detosylation of cyclo(-L-aminoacyl-L-Ser-), which were synthesized via the Nitecki and Fischer methods. Hydrogenation of the double bond of dehydroalanine residues in cyclodipeptides was carried out using Pd black in methanol at 1-atm pressure and room temperature. The degree of asymmetric hydrogenation was assessed by determining the amounts of L- and D-alanine by a modified Manning and Moore procedure. When L-valine was used as a chiral source, L-alanine residue with chiral induction of 98.4% was derived from cyclo(-L-Val-deltaAla-). L-Amino acids other than L-proline also were effective in inducing remarkable asymmetric hydrogenation. Hydrogenation of alpha,beta-dehydro-alpha-aminobutanoic acid residues in cyclodipeptides produced L-alpha-aminobutanoic acid residues with effective chiral induction to the same extent as observed with dehydroalanine residues. Optically pure l-alanine was prepared from cyclo(-L-Lys(epsilon-Ac)-deltaAla-) via asymmetric hydrogenation. A mechanism of chiral induction is discussed.

Alanine↗
PubMed1977

Synthetic identification as a hexapeptide of alpha substance-IB inducing sexual agglutination in Saccharomyces cerevisiae.

For the identification of a peptidyl principle inducing sexual agglutination in the yeast, 2 supposed hexapeptides (1a, b) were synthesized by the conventional method. The 1a (H-Arg-Gly-Pro-Phe-Pro-Ile-OH) revealed complete identity with the natural peptide in TLC, MS and biological property on agglutination. The 1b showed the sexual agglutinability in the same degree as 1a, though distinct differences were observed in the chemical data. Both 1a and 1b had a strong bitter taste.

Agglutination↗
PubMed1977

Studies on the synthesis of proteinase inhibitors. I. Synthesis and activity of nonapeptide fragments of soybean Bowman-Birk inhibitor.

Two heterodetic cyclic nonapeptides, X-Cys-Thr-Lys-Ser-Asn-Pro-Pro-Gln-Cys-Y (Ia: X = Ac, Y = NH2; Ib: X = H, Y = OH), which correspond to residues 14-22 in the sequence of Bowman-Birk inhibitor, have been synthesized by Merrifield's solid-phase method. Inhibitory activities of Ia and Ib on tryptic hydrolysis of amide and ester substrates were examined. When Gly2-Lys-Gly3 and Tos-Arg-OMe were used as substrates, the values of I50 for the peptide Ia were calculated to be 3.6 micron and 40 micron, respectively. When Gly2-Lys-Gly3 was used as a substrate, the value of Ki was calculated to be 1.5 micron. Ia was hydrolyzed slowly by trypsin, losing the inhibitory activity. When the Lys-Ser bond of Ia was cleved with trypsin, the modified Ia could not be regenerated by trypsin. The linear peptide S, S'-dicarboxamidomethyl-Ia also was inactive and appeared to be a good substrate. Optical rotatory dispersion studies showed that the active fragments have characteristic conformations which were lost upon modification to inactive derivatives.

Chromatography, Gel↗
PubMed1977

Cyclic peptides. II. Synthesis of AM-Toxin I.

To confirm the structure of AM-toxin I (a phytotoxic cyclotetradepsipeptide) the proposed peptide was prepared by a conventional method. The synthetic peptide and natural AM-toxin I were identical as regards t.l.c., u.v., mass spectra and biological activity in causing necrosis on apple leaves. A prepared dimer of AM-toxin I showed extremely weak activity; the relationship between the ring size and biological activity of AM-toxin I is discussed.

Mass Spectrometry↗
PubMed1977

Cylic peptides. I. Synthesis of AM-toxin analog containing O-methyl-l-tyrosine.

An AM-toxin analog, cyclotetradepsipeptide, containing an O-methyl-L-tyrosine residue in place of an L-2-amino-5-arylpentanoic acid residue in AM-toxins has been prepared by a conventional method. The synthesis was attempted through six different routes and the desired analog was obtained by one such procedure. This compound showed extremely weak activity in causing necrosis on apple leaves.

Amino Acid Sequence↗
PubMed1976

Interaction of dopamine, methyldopa and reserpine in the sympatho-adrenal system in essential hypertension.

1. The interactions of dopamine, reserpine and methyldopa on blood pressure of normal subjects and of those with essential hypertension were examined. 2. When biosynthesis of noradrenaline from dopamine was blocked by reserpine, dopamine induced a prominent depressor effect in essential hypertension. 3. The long-term treatment with methyldopa induced a marked potentiateion of the pressor action of domapine in hypertension, although no significant pressor response was found in normal subjects. 4. It is suggested that methylnoradrenaline may accumulate in peripheral nerve endings of patients with essential hypertension in comparison with normal subjects, and this accumulated methylnoradrenaline potentiates the pressor response to dopamine in essential hypertension.

Adult↗