Dipeptides of the Unnaturally Occurring d-Amino Acids

Smith, C. S.; Brown, Amy

doi:10.1021/ja01855a020

Cited by 23 publications

(5 citation statements)

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“…88-890 and discuss the reasons for the higher values reported by earlier authors (e.g. 126-128°given by Smith & Brown, 1941) (Found: C, 69-7; H, 5-8; N, 4*8. Cale.…”

Section: Methodsmentioning

confidence: 65%

The pH-dependence of pepsin-catalysed reactions

Cornish‐Bowden

Knowles

1969

Biochemical Journal

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1. The pH-dependence of the pepsin-catalysed hydrolysis of three peptide substrates was studied by using a method for the continuous monitoring of the formation of ninhydrin-positive products. 2. Two peptide acid substrates, N-acetyl-l-phenylalanyl-l-phenylalanine and N-acetyl-l-phenylalanyl-l-phenylalanyl-glycine, show apparent pK(a) values of 1.1 and 3.5 in the plots of k(0)/K(m) versus pH. By contrast a neutral substrate, N-acetyl-l-phenylalanyl-l-phenylalanine amide, shows apparent pK(a) values of 1.0 and 4.7. 3. Together with the data of the preceding paper (Knowles, Sharp & Greenwell, 1969), these results are taken to indicate that the rate of pepsin-catalysed hydrolysis is controlled by the ionization of two groups, which on the free enzyme have apparent pK(a) values of 1.0 and 4.7. It is apparent that the anions of peptide acid substrates are not perceptibly bound to the enzyme, resulting in apparent pK(a) values of 3.5 for the dependence of k(0)/K(m) for these materials.

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“…88-890 and discuss the reasons for the higher values reported by earlier authors (e.g. 126-128°given by Smith & Brown, 1941) (Found: C, 69-7; H, 5-8; N, 4*8. Cale.…”

Section: Methodsmentioning

confidence: 65%

The pH-dependence of pepsin-catalysed reactions

Cornish‐Bowden

Knowles

1969

Biochemical Journal

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“…l -Leucine Methyl Ester ( LeuC 1 ) . Under a dry atmosphere, thionyl chloride (15.0 g, 126 mmol) was added dropwise, with stirring, over a period of 10 min, to 50 mL of absolute methanol which was cooled by an ice-salt bath (ca.…”

Section: Methodsmentioning

confidence: 99%

“…l -Isoleucine Methyl Ester ( IleC 1 ). Yield: 37% of a clear liquid of 99% purity (GC), bp 34−35 °C/0.5 Torr. IR: 3386, 3313, 2963, 2935, 2877, 1735, 1619, 1459, 1436 cm -1 .…”

Section: Methodsmentioning

confidence: 99%

Reversible, Room-Temperature, Chiral Ionic Liquids. Amidinium Carbamates Derived from Amidines and Amino-Acid Esters with Carbon Dioxide

et al. 2007

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The properties of a new class of chiral, room-temperature, ionic liquids (RTILs) are described. They are made from easily synthesized, readily available materials and can be transformed reversibly to their nonionic liquid states. The nonionic liquids consist of neat equimolar mixtures of a N′-alkyl-N,Ndimethylacetamidine (L) and an alkyl ester of a naturally occurring amino acid (n). When exposed to 1 atm of CO 2 gas, the L/n solutions become cationic-anionic pairs, amidinium carbamates. Of the 50 L/n combinations examined, all except those involving the methyl ester of tyrosine (which was immiscible with the amidines) form RTIL states under CO 2 atmospheres, and several remain liquids to at least -18 °C. Heating the ionic liquids in air at ca. 50 °C or bubbling N 2 gas through them at ambient temperatures for protracted periods displaces the CO 2 and re-establishes the nonionic L/n states. As an example of the changes effected by cycling between the two liquid states, a spectroscopic probe, 1-(pdimethylaminophenyl)-2-nitroethylene, senses a polarity like that of toluene before a mixture of N′octyl-N,N-dimethylacetamidine/isoleucine methyl ester is exposed to CO 2 and a polarity like that of N,Ndimethylformamide afterward; whereas a low-polarity solvent, decane, is solublized readily by the nonionic L/n mixture, it is immiscible with the RTIL. Thermal and spectroscopic properties of both the nonionic and ionic phases are reported and compared. Several possible applications for these RTILs can be envisioned because, unlike many other ionic liquids, these need not be prepared and handled under scrupulously dry conditions and they can be cycled repeatedly between high-and low-polarity states.

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“…The melting point of the purified product is 120-122°. Bergmann et al (11) found 121°while Smith and Brown (10) reported that carbobenzoxy-d(+)-leucine hydrazide melted at 121°. Carbobenzoxy-l-(-)-leucine azide (12).…”

Section: T H I S C O N T E N T Imentioning

confidence: 99%

“…The twice recrystallized product is free of Z(-)-leucine hydrochloride and melts at 150-151°. Smith and Brown (10) reported the melting point 149-150°for <Z(+)-leucine methyl ester hydrochloride.…”

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confidence: 99%

THE SYNTHESIS OF l(—)-LEUCYLGLYCYLGLYCINE¹

Schott¹,

LARKIN²,

Rockland³

et al. 1947

J. Org. Chem.

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The preparation of relatively large quantities of a number of peptides (2, 3) required for certain enzyme studies during the war period was undertaken in the writers' laboratory. The preparation of l(-)-leueylgIycylglycine is described in the present report, since there are no entirely adequate literature methods for the synthesis of this tripeptide. The only recorded synthesis is that of Abderhalden and Fodor (4) who prepared 2.5 g. of the crude peptide by amination of d-a-bromoisocapronylglycylglycine. The latter compound was synthesized by the reaction of d-a-bromoisocapronyl chloride and glycine anhydride. The preparation of less than 1 g. of carbobenzoxy-Z( -)-leucylglycylglycine by the hydrazide procedure has been described by Bergmann et al. (5). EXPERIMENTAL 9,B-Diketopiperazine (glycine anhydride). This method is a modification of that described by Sannié (6). A mixture containing 700 g. of technical glycine and 3500 ml. of technical ethylene glycol is heated for 50 minutes at 174-176°with continuous stirring in a 5-1. round-bottom flask. The mixture is cooled for 20 hrs. in the refrigerator, the suspension is centrifuged and the brown crystalline precipitate is washed on a Büchner funnel with absolute methanol (1500 ml. total volume) until the washings are nearly colorless. The brown-colored 2,5-diketopiperazine (about 320 g.) is dissolved in 2.2 1. of boiling water and the solution is cooled overnight in the refrigerator. The suspension is filtered and the light brown crystals are washed with absolute methanol (500 ml.) and dried in air. The product (about 250 g.) is dissolved in 2.5 1. of boiling water, the solution is decolorized with 20 g. of carbon (Nuchar XXX) and the suspension is filtered on a steam-heated Büchner funnel.

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Dipeptides of the Unnaturally Occurring d-Amino Acids

Cited by 23 publications

References 0 publications

The pH-dependence of pepsin-catalysed reactions

The pH-dependence of pepsin-catalysed reactions

Reversible, Room-Temperature, Chiral Ionic Liquids. Amidinium Carbamates Derived from Amidines and Amino-Acid Esters with Carbon Dioxide

THE SYNTHESIS OF l(—)-LEUCYLGLYCYLGLYCINE¹

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Dipeptides of the Unnaturally Occurring d-Amino Acids

Cited by 23 publications

References 0 publications

The pH-dependence of pepsin-catalysed reactions

The pH-dependence of pepsin-catalysed reactions

Reversible, Room-Temperature, Chiral Ionic Liquids. Amidinium Carbamates Derived from Amidines and Amino-Acid Esters with Carbon Dioxide

THE SYNTHESIS OF l(—)-LEUCYLGLYCYLGLYCINE1

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THE SYNTHESIS OF l(—)-LEUCYLGLYCYLGLYCINE¹