- Unusual Enhancement of Protease Activity in Organic Solvents by Amines
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The catalytic activities of subtilisin BPN' and α-chymotrypsin for transesterification of N-acetyl-L-tyrosine methyl ester in organic solvents were dramatically increased by addition of tertiary amines.The effects may be ascribed to the change in dissociation state of polar groups on the surface of the enzymes.
- Yamamoto, Yasuhito,Kise, Hideo
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Read Online
- Fluorescence Spectroscopic Study of α-Chymotrypsin as Relevant to Catalytic Activity in Aqueous-Organic Media
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The effects of the composition of aqueous-organic mixed solvents on steady state fluorescence emission of α-chymotrypsin were investigated.In all the solvent systems, maximum wavelength of fluorescence emission shifted initially to higher wavelength and then to lower wavelength by increasing water content in organic solvents.The results were interpreted in terms of the changes in microenvironment of tryptophan residues in the enzyme due to conformational modification of the enzyme.The maximoum emission wavelength of chymotrypsin is well correlated to its catalytic activity for the hydrolysis of N-acetyl-L-tyrosine ethyl ester.Activity of chymotrypsin decreased or it was totally inhibited at solvent compositions which give long emission wavelength of the enzyme.The results suggest that the fluorescence spectroscopy may be useful for detection of conformational chnges and alternation of catalytic activity of the enzyme.
- Tomiuchi, Yoshimasa,Kijima, Tatsurou,Kise, Hideo
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Read Online
- Effect of dioxane on the binding of competitive inhibitor proflavin and catalytic activity of bovine pancreatic α-chymotrypsin
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The binding of competitive inhibitor proflavin by α-chymotrypsin in water-dioxane mixtures over the entire range of thermodynamic activities of water a w was studied. The data on the degree of binding of proflavin were compared to the results on the catalytic activity of the enzyme preliminary incubated in water-dioxane mixtures. An analysis of the behavior of the concentration dependences of these characteristics demonstrated that, at low a w values, the behavior of the interprotein contacts in the enzyme formed during its drying largely governs its functional properties, while at high a w values, they are determined by the interaction of the enzyme with the organic solvent. Interplay of these two factors is responsible for the observed complex shape of the isotherm of binding of proflavin, with the maximum degree of binding being attained at moderate a w values.
- Sirotkin,Mukhametzyanov,Karmanova
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Read Online
- Structure-activity relationship studies of dipeptide-based hepsin inhibitors with Arg bioisosteres
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Hepsin is a type II transmembrane serine protease (TTSP) associated with cell proliferation and overexpressed in several types of cancer including prostate cancer (PCa). Because of its significant role in cancer progression and metastasis, hepsin is an attractive protein as a potential therapeutic and diagnostic biomarker for PCa. Based on the reported Leu-Arg dipeptide-based hepsin inhibitors, we performed structural modification and determined in vitro hepsin- and matriptase-inhibitory activities. Comprehensive structure-activity relationship studies identified that the p-guanidinophenylalanine-based dipeptide analog 22a exhibited a strong hepsin-inhibitory activity (Ki = 50.5 nM) and 22-fold hepsin selectivity over matriptase. Compound 22a could be a prototype molecule for structural optimization of dipeptide-based hepsin inhibitors.
- Kwon, Hongmok,Ha, Hyunsoo,Jeon, Hayoung,Jang, Jaebong,Son, Sang-Hyun,Lee, Kiho,Park, Song-Kyu,Byun, Youngjoo
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supporting information
(2020/12/25)
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- GRANZYME B DIRECTED IMAGING AND THERAPY
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Provided herein are heterocyclic compounds useful for imaging Granzyme B. Methods of imaging Granzyme B, combination therapies, and kits comprising the Granzyme B imaging agents are also provided.
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Page/Page column 82; 98
(2019/09/04)
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- Photoinduced electron transfer-promoted debenzylation of phenylalanine and tyrosine derivatives using dicyanoarene
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Photoinduced debenzylations of phenylalanine and tyrosine derivatives with dicyanoarenes afford glycine derivatives by the generation of radical cations. Despite the limited substrate scope, the radical cation of phenylalanine and tyrosine derivatives bearing both a carbamate (without an aromatic group) at the N-terminal and an amide at the C-terminal could promote the breaking C–C bond at the benzylic position by a photoinduced electron transfer. It is important to understand the chemical behavior of the radical cations of phenylalanine and tyrosine in enzymes involving electron transfer.
- Yamawaki, Mugen,Okita, Yoshiki,Yamamoto, Takashi,Morita, Toshio,Yoshimi, Yasuharu
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p. 7239 - 7244
(2017/11/20)
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- Radical arylation of tyrosine residues in peptides
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The radical arylation of the phenolic side chain of tyrosine in peptides was investigated. Aryl radicals were generated from aryldiazonium salts using titanium(III) chloride as stoichiometric reductant. Due to the high selectivity with which 3-aryltyrosine derivatives were formed, this reaction type represents a new strategy for the direct functionalization of peptides.
- Fehler, Stefanie K.,Pratsch, Gerald,?streicher, Christiane,Fürst, Michael C.D.,Pischetsrieder, Monika,Heinrich, Markus R.
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supporting information
p. 7888 - 7893
(2016/11/17)
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- Peptide Tyrosinase Activators
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Peptides that increase melanin synthesis are provided. These peptides include pentapeptides YSSWY, YRSRK, and their variants. The peptides may activate the enzymatic activity of tyrosinase to increase melanin synthesis. The pharmaceutical, cosmetic, and other compositions including the peptides are also provided. The methods of increasing melanin production in epidermis of a subject are provided where the methods include administering compositions comprising an amount of one or more peptides effective to increase the melanin production. The methods also include treating vitiligo or other hypopigmentation disorders with compositions including one or more peptides.
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- Oxidative damage of aromatic dipeptides by the environmental oxidants NO2 and O3
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Irreversible oxidative damage at both aromatic side chains and dipeptide linkage occurs in the aromatic N- and C-protected dipeptides 7-11 upon exposure to the environmental pollutants NO2 and O3. The reaction proceeds through initial oxidation of the aromatic ring by in situ generated NO3, or by NO2, respectively, which leads to formation of nitroaromatic products. The indole ring in Phe-Trp undergoes oxidative cyclization to a pyrroloindoline. An important reaction pathway for dipeptides with less oxidisable aromatic side chains proceeds through fragmentation of the peptide bond with concomitant acyl migration. This process is likely initiated by an ionic reaction of the amide nitrogen with the NO2 dimer, N2O4. This journal is
- Gamon,White,Wille
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supporting information
p. 8280 - 8287
(2015/01/08)
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- Hydrogen/deuterium exchange of cross-linkable α-amino acid derivatives in deuterated triflic acid
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In this paper we report here a hydrogen/deuterium exchange (H/D exchange) of cross-linkable α-amino acid derivatives with deuterated trifluoromethanesulfonic acid (TfOD). H/D exchange with TfOD was easily applied to o-catechol containing phenylalanine (DOPA) within an hour. A partial H/D exchange was observed for trifluoromethyldiazirinyl (TFMD) phenylalanine derivatives. N-Acetyl-protected natural aromatic α-amino acids (Tyr and Trp) were more effective in H/D exchange than unprotected ones. The N-acetylated TFMD phenylalanine derivative afforded slightly higher H/D exchange than unprotected derivatives. An effective post-deuteration method for cross-linkable α-amino acid derivatives will be useful for the analysis of biological functions of bioactive peptides and proteins by mass spectrometry.
- Wang, Lei,Murai, Yuta,Yoshida, Takuma,Okamoto, Masashi,Masuda, Katsuyoshi,Sakihama, Yasuko,Hashidoko, Yasuyuki,Hatanaka, Yasumaru,Hashimoto, Makoto
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p. 1129 - 1134
(2015/07/20)
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- Resolution of N-protected amino acid esters using whole cells of Candida parapsilosis ATCC 7330
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Whole cells of Candida parapsilosis ATCC 7330 were used for the resolution of N-acetyl amino acid esters. Excellent enantioselectivities (E = 40 to >500) were achieved for the resolution of N-protected protein and non-protein amino acid esters giving good yields (28-50%) and high enantiomeric excesses (up to >99%) for both enantiomers.
- Stella, Selvaraj,Chadha, Anju
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experimental part
p. 457 - 460
(2010/06/21)
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- Discovery of hydrolytic catalysts in a peptidocalixarene library by binding assay with a transition state analogue for the hydrolysis
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Hydrolytic catalysts were found in a peptidocalixarene library by binding assay with a transition state analogue for the hydrolysis. The rate of the reaction can be specifically enhanced up to 50-fold in the presence of the discovered catalyst. The Royal
- Hioki, Hideaki,Nishimoto, Ryosuke,Kawaguchi, Kota,Kubo, Miwa,Harada, Kenichi,Fukuyama, Yoshiyasu
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supporting information; experimental part
p. 7194 - 7196
(2010/03/25)
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- Chemoenzymatic synthesis of l-tyrosine derivative for a transketolase assay
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We have prepared an l-tyrosine derivative bearing a d-threo ketose moiety by a convenient chemoenzymatic route. This compound is of potential interest for developing stereospecific assays for enzymes catalyzing C-C bond cleavage such as transketolase. We showed in vitro by analytical studies (LC/MS and 31P NMR) that this compound can release l-tyrosine in the presence of wild type TK extract and bovine serum albumin. This assay is the first step towards a mutant TK selection test that could be developed for yeast cells auxotrophic for l-tyrosine.
- Charmantray, Franck,Hélaine, Virgil,Làsikovà, Angelika,Legeret, Bertrand,Hecquet, Laurence
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p. 3229 - 3233
(2008/09/21)
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- Process for preparation of tamsulosin and its aralkylamine derivatives
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The present invention discloses a new process for the synthesis of tamsulosin and its aralkylamine derivatives, especially (R)-(?)-5-{2-[2-(2-alkoxyphenoxy)ethylamino]propyl}-2-alkoxybenzenesulfonamides having the following formula 1 (where R1 and R2 represent C1-C4 alkyl groups) and their hydrochloride thereof, and other various pharmaceutical used salts. Tamsulosin hydrochloride (R1=Et, R2=Me, in its hydrochloride salt form) is an antagonist of α-A adrenoceptors in the prostate. Tamsulosin?HCl occurs as white crystals, which melt with decomposition at approximately 230° C. It is sparingly soluble in water and in methanol, slightly soluble in glacial acetic acid and in ethanol, and practically insoluble in ether.
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Page/Page column 2; 4
(2008/06/13)
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- FUNCTIONALIZED AMINO ACIDS AND ABSORBABLE POLYMERS THEREFROM
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The present invention relates to compounds of formula I and II, which are functionalized amino acids, and polymers formed from the same. Polymers formed from the functionalized amino acids are expected to have controllable degradation profiles, enabling them to release an active component over a desired time range. The polymers are also expected to be useful in a variety of medical applications.
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Page/Page column 39-40
(2008/06/13)
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- FUNCTIONALIZED DIPHENOLICS AND ABSORBABLE POLYMERS THEREFROM
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The present invention relates to dephenolic compounds, an example of which is shown below, which are functionalized, and polymers formed from the same. Polymers formed from the functionalized diphenolics are expected to have controllable degradation profiles, enabling them to release an active component over a desired time range. The polymers are also expected to be useful in a variety of medical applications.
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Page/Page column 24
(2008/06/13)
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- Process for preparation of tamsulosin and its derivatives
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The present invention discloses a new process for the synthesis of tamsulosin derivatives of formula 1 (where R 1 and R 2 represent C 1 -C 4 alkyl groups) and their hydrochlorides and other pharmaceutically acceptable salts, comprising reacting the hydrochloride of sulphonamide 2 (where R represents C 1 -C 4 alkyl) with the ether compound 21 (where R' represents C 1 -C 4 alkyl and R" represents MeC 6 H 4 SO 2 or MeSO 2 ).
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Page/Page column 4; 7
(2008/06/13)
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- NOVEL INTERMEDIATES FOR THE SYNTHESIS OF (R)-TAMSULOSIN AND OF ITS PHARMACEUTICALLY ACCEPTABLE SALTS AND PROCESS FOR THEIR PREPARATION
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A subject matter of the present invention is novel intermediates for the synthesis of (R)-tamsulosin and of its pharmaceutically acceptable salts, and also the associated preparation process.
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Page/Page column 21
(2008/06/13)
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- PROCESSES FOR MAKING THIAZOLIDINEDIONE DERIVATIVES AND COMPOUNDS THEREOF
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A compound of the formula (I): wherein A represents a ring group connected to the oxygen atom by a C1 to C6 hydrocarbon chain, R is hydrogen or a C1-C4 alkyl, and Q is hydrogen, or an amine protecting group such as acetyl, trifluoroacetyl, benzoyl, benzyl, or trityl, is useful in making thiazolidinedione derivatives (formula (II)), such as pioglitazone, rosiglitazone and troglitazone.
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- Synthesis of N,N-dimethyl-2,4-dinitro-5-fluorobenzylamine and its reactions with amino acids and peptides
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A practical synthesis is described for N,N-dimethyl-2,4-dinitro-5- fluorobenzylamine (DMDNFB) and its -d6 analog as an alternative Sanger's reagent (DNFB), for purposes of amino acid derivatization detectable by positive mode electrospray ionization mass spectrometry. DMDNFB is comparable to DNFB in its efficiency to derivatize amino acids and peptides. Various DMDNP (d0/d6) derivatives of (modified) lysine were synthesized to evaluate the potential use of isotope-edited LC-ESI-MS as a tool for structural definition of the posttranslational modification of protein-based lysines.
- Liu, Zhongfa,Sayre, Lawrence M.
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p. 1601 - 1610
(2007/10/03)
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- Low molecular weight components of cartilage, complexes of metals with amino acids, DI-peptides and analogs thereof; processes for preparation and therapeutic uses thereof
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Low molecular weight components extracted from shark cartilage and complexes made of copper with amino acid or dipeptide units or analogs thereof are disclosed. Methods are disclosed for the inhibition of angiogenesis (neovascularization) in an animal through the administration of these complexes, which results in treating angiogenesis-dependent diseases.
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- Effect of freezing on the enzymatic coupling of specific amino acid-containing peptide fragments
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The effect of freezing on the enzymatic coupling of highly specific amino acid-containing peptide fragments was investigated using trypsin, α-chymotrypsin, and Bacillus licheniformis Glu-specific endopeptidase as biocatalysts. Comparison with reactions at normal temperature indicates that freezing efficiently represses the cleavage of specific peptide bonds independent of their individual localisation and specificity achieving irreversible and efficient peptide bond formation without proteolytic side reactions. Copyright (C) 2000 Elsevier Science Ltd.
- Wehofsky, Nicole,Haensler, Marion,Kirbach, Sebastian W.,Wissmann, Johannes-Dieter,Bordusa, Frank
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p. 2421 - 2428
(2007/10/03)
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- Solid-state proton/sodium buffers: Chemical pH stats for biocatalysts in organic solvents
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The useful application of enzymes in organic synthesis requires reliable and straightforward methods for maximising efficiency and selectivity. Here we describe how to control the protonation state of enzymes using a new class of solid-state buffers, applied for the first time in polar organic solvents. Remarkably these insoluble buffers are able to rapidly exchange H+ and Na+ ions with both the protein and reaction mixture as demonstrated here using propanol rinsed enzyme preparations (PREPs) of subtilisin Carlsberg and chymotrypsin. The buffers tested were generally mixtures of a zwitterionic biological buffer and its Na+ salt with each buffer pair setting a characteristic fixed ratio of H+ activity to Na+ activity (aH+/aNa+) within the system. Dependent upon the solid buffer pair selected a wide range of different enzymatic activities could be observed. The variation in rate showed a fairly good but not exact correlation with the aqueous pKa of the buffers, indicating that crystal lattice energies have less affect on acid-base strength than might be expected. The solid-state buffers were able to prevent detrimental changes to enzyme activity caused by the presence or build up of acids or bases in the organic reaction mixture (often undetected). They could also be used advantageously to tune the enzyme protonation state in solvent if a previous aqueous preparation step needs to be carried out at a pH not optimal for catalysis. Such buffering systems are expected to find wide-spread use as 'chemical pH stats' for reactions in non-aqueous media.
- Partridge, Johann,Halling, Peter J.,Moore, Barry D.
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p. 465 - 471
(2007/10/03)
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- Effects of metal salts on the structure and activity of α-chymotrypsin in ethanol/water
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The catalytic activity and circular dichroic (CD) spectra of α- chymotrypsin (CT) were measured in ethanol/water (95/5, v/v) solution containing small amounts of metal salts. Although the catalytic activity of CT increased upon the addition of all the metal salts used, the magnitude of activity increase was different for different metal salts. Especially, calcium acetate accelerated the transesterification of amino acid up to 6 fold at 100 μM. The secondary and tertiary structures of CT were also changed by metal salts, as studied by CD measurements. The effects of metal salts on the stability of CT in ethanol/water were also studied, and it was found that the residual activity of CT after 7 days in ethanol/water in the presence of Ca(OCOCH3)2 was about 20% of the initial activity. The change in activity was closely correlated with the change in the mean residue ellipticity of CT at 208 or 230 nm.
- Sasaki, Toshiya,Kise, Hideo
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p. 1321 - 1325
(2007/10/03)
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- Pronase catalysed peptide syntheses
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A mixture of proteases from Streptomyces griseus (pronase), displaying a very broad substrate tolerance in the hydrolysis of peptides, has been studied for the first time systematically regarding their substrate specificity in peptide synthesis. It is demonstrated that pronase can be employed successfully for the formation of dipeptides with yields up to 95%. Pronase has also been employed successfully as catalyst for the enzyme assisted synthesis of a hexapeptide.
- Lobell, Mario,Schneider, Manfred P.
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p. 319 - 325
(2007/10/03)
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- Acylase I catalysed hydrolysis of para-substituted (S)-phenylalanine derivatives from mixtures of the racemic ortho- and para-substituted isomers
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para-Substituted (S)-phenylalanines may be obtained by treatment of the corresponding mixtures of ortho- and para-substituted N-acetyl-(RS)- phenylalanines with Acylase I from porcine kidney. The selectivity of the enzyme may be attributed to its evolution to digest peptide derivatives of (S)-phenylalanine and (S)-tyrosine.
- Easton, Christopher J.,Harper, Jason B.
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p. 5269 - 5272
(2007/10/03)
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- Cross-linked crystals of subtilisin: Versatile catalyst for organic synthesis
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Cross-linked enzyme crystals (CLECs) of subtilisin exhibit excellent activity in aqueous and various organic solvents. This catalyst is more stable than the native enzyme in both aqueous and mixed aqueous/organic solutions. Subtilisin-CLEC was shown to be a versatile catalyst. It was used for the syntheses of peptides and peptidomimetics, mild hydrolysis of amino acid and peptide amides, enantio- and regioselective reactions, and transesterifications.
- Wang, Yi-Fong,Yakovlevsky, Kirill,Zhang, Bailing,Margolin, Alexey L.
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p. 3488 - 3495
(2007/10/03)
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- Enantioselective hydrolytic reactions of rice bran lipase (RBL): A first report
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Enantioselectivity has been observed in the hydrolysis of racemic N-acetyl amino acid esters with rice bran lipase (RBL). The enzyme shows selectivity towards the (S)-enantiomer. Products with high enantiomeric excess (e.e. >99%) are obtained depending upon the hydrophobicity of the amino acid as well as that of the leaving group.
- Fadnavis,Jadhav, Vasudev
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p. 2361 - 2366
(2007/10/03)
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- Cosmetic composition
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A composition suitable for topical application to mammalian skin and hair for inducing, maintaining or increasing hair growth comprises a hair growth promoter chosen from glutamine derivatives and salts thereof. The composition preferably also comprises an activity enhancer which may be chosen from hair growth stimulants, penetration enhancers and cationic polymers.
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- A novel tea-bag methodology for enzymatic resolutions of α-amino acid derivatives in reverse micellar media
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A novel tea bag methodology for resolution of methyl esters of N-acetyl- α-amino acids in reverse micellar medium of bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) in isooctane-chloroform using immobilized enzymes or microbial cells is presented. The methodology effectively solves the problems of substrate solubility, product separation and surfactant recycling and provides products in high yields (80 to 90%) and excellent optical purities (% ee 97 to >99%).
- Bhalerao,Rao,Fadnavis
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p. 2109 - 2118
(2007/10/02)
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- Cosmetic composition containing DOPA derivatives
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A composition for topical application to human hair or skin contains a chemical analogue of dihydroxyphenyl alanine (DOPA). This chemical analogue can be absorbed by skin or by a hair follicle and metabolised in-vivo, thus leading to the formation of melanin in skin or to the growth of melanin-pigmented hair. Consequently the composition can give controlled skin darkening to mimic sun-induced tanning or can bring about the growth of dar hair in place of the grey or white hair.
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- Concentration- and Structure-Dependent Effects of Amides on Protease Activity in Organic Solvents
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The catalytic activity of α-chymotrypsin (CT) in the transesterification of N-acetyl-L-tyrosine methyl ester to its ethyl ester in aqueous-organic media was markedly enhanced by replacing a part of water with foramide.The activity of CT was strongly dependent on the formamide/water ratio, and excess formamide retarded the activity.Addition of formamide to reaction mixtures at constant water contents exhibited similar activation-deactivation profiles for CT.A kinetic study revealed that the rate acceleration is due to an increase in kcat rather than a change in Km.At a given concentration of amides (0.5 M, M = mol dm-3), propionamide and DMF were much less effective than formamide for activation of CT.The results suggest that foramide interacts with CT in a different way from water.
- Yamamoto, Yasuhito,Kise, Hideo
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p. 1367 - 1370
(2007/10/02)
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- Selectivity and Specificity in Substrate Binding to Proteases: Novel Hydrolytic Reactions Catalysed by α-Chymotrypsin Suspended in Organic Solvents with Low Water Content and Mediated by Ammonium Hydrogen Carbonate
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α-Chymotrypsin suspended in organic solvents with low water content catalysed hydrolytic reactions in the presence of ammonium hydrogen carbonate.Molecular modelling studies were carried out and structure-reactivity relationships were established by studying the hydrolysis of amino acid derivatives and analogues.The enzyme was found to be stereoselective with respect to the hydrolysis of L-amino acid derivatives, but no stereoselectivity was observed when α-hydroxy esters were used as substrates.A general procedure for the resolution of aromatic amino acid esters is given.The results are interpreted in terms of molecular modelling based on X-ray crystallographic data and literature data.
- Ricca, Jean-Marc,Crout, David H. G.
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p. 1225 - 1234
(2007/10/02)
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- Cosmestic composition
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A composition suitable for topical application to mammalian skin and hair for inducing, maintaining or increasing hair growth comprises a hair growth promoter chosen from glutamic acid derivatives and salts thereof. The composition preferably also comprises an activity enhancer which may be chosen from hair growth stimulants, penetration enhancers and cationic polymers.
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- Synthesis and application of (3R,4R)-3,4-bis(diphenylphosphino)tetrahydrofuran as ligand for asymmetric hydrogenation of acrylic acids
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A new, chiral bisphosphine, (3R,4R)-3,4-bis(diphenylphosphino)tetrahydrofuran (4), is synthesized in three steps from (R,R)-tartaric acid esters. With rhodium(I) complexes of 4 enantiomeric excesses of 54 to 97% are obtained on catalytic hydrogenation of 2-(acetylamino)acrylic acid, 2-(acetylamino)cinnamic acids and itaconic acid. The applied substrate/catalyst ratios were between 250:1 and 11,000:1.
- Terfort
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p. 951 - 953
(2007/10/02)
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- Hair growth composition containing citric acid esters
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Triesters of citric acid are used for inducing, maintaining or increasing hair growth. Compositions for topical application to mammalian hair or scalp comprise an effective amount of from 1% to 99% by weight of an ester of citric acid having the structure (1): where, R1, R2 and R3 each independently represent a branched or unbranched alkyl, alkenyl, aryl, alkylaryl or arylalkyl group, each said group having from 1 to 18 carbon atoms, R4 represents -H, or a branched or unbranched saturated or unsaturated acyl, alkyl, aryl, alkylaryl or aylalkyl group having from 1 to 18 carbon atoms, in the presence of a cosmetically acceptable vehicle for the citric acid ester and in the absence of solid absorbent for the ester;, said effective amount of said ester being sufficient to increase hair growth in the rat, when said composition is applied topically thereto over a period of no more than three months, by at least 10% more than that obtainable using a control composition from which the said ester has been omitted, in accordance with the Rat Hair Growth Test.
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- Cosmetic composition
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A composition suitable for topical application to mammalian skin and hair for inducing, maintaining or increasing hair growth comprises a hair growth promoter chosen from N-acylated amino-acids, in which the acyl group has from 2 to 20 carbon atoms, together with a cosmetically acceptable vehicle for the hair growth promoter.
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- Efficient Asymmetric Hydrogenations of (Z)-2-Acetamidoacrylic Acid Derivatives with the Cationic Rhodium Complex of (2S,4S)-MOD-BPPM
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The preparation of (2S,4S)-MOD-BPPM ((2S,4S)-N-(t-butoxycarbonyl)-4-phosphino>-2-phosphino>methyl>pyrrolidine) and its application to highly effective asymmetric hydrogenations of (Z)-2-acetamidoacrylic acid derivatives are described.
- Takahashi, Hisashi,Achiwa, Kazuo
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p. 305 - 308
(2007/10/02)
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- PEPTIDE SYNTHESIS CATALYZED BY NATIVE PROTEINASE K IN WATER-MISCIBLE ORGANIC SOLVENTS WITH LOW WATER CONTENT
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Rection of Ac-Tyr-OEt with HBr.Gly-NH2, catalysed by free proteinase K in various water-miscible organic solvents in the presence of triethylamine and 5 mol percent of water, was studied.Some aliphatic alcohols and acetonitrile proved to be suitable solvents.The effect of water content (2 percent - 20 percent) on the synthesis of Ac-Tyr-Gly-NH2 was studied using acetonitrile as solvent.Lowering of the water content to 5 percent or 2 percent led to almost 100 percent yield of the desired dipeptide; higher water content accelerated the reaction reducing at the same time the yield of Ac-Tyr-Gly-NH2 due to the concurrent hydrolysis of the ester Ac-Tyr-OEt.No reaction was observed in the absence of base (triethylamine), wereas an excess of base only retarded the reaction.The enzyme is capable of catalyzing the peptide bond synthesis with N-acylamino acids or N-acyl peptides as acylating components, which may contain all types of L-amino acid residues (except Pro) in the P1 position.However, the peptide bond synthesis depends strongly on the amino component composition, particularly on the amino acid residue in the P'1 position.Only amides of glycine and of hydrophillic amino acids were acylated with Ac-Tyr-OEt; amides of hydrophobic amino acids enter the reaction only reluctantly or not at al.The presence of Leu or Phe in position P'2 and Leu in position P'3 has not so negative effect on acylation of the amino component as has in presence in the P'1 position.The choice of protecting groups for the α-carboxyl of the amino component is restricted only to amide and in some cases its undesired enzymatic removal was observed.Unprotected peptides seem to be suitable amino components.
- Cerovsky, Vaclav,Martinek, Karel
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p. 2027 - 2041
(2007/10/02)
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- FREE CHYMOTRYPSIN-CATALYZED SYNTHESIS OF PEPTIDE BOND AN ALIPHATIC ALCOHOLS WITH LOW WATER CONTENT
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The effect of water content on free chymotrypsin-catalyzed reaction of Ac-Tyr-OEt with HBr*Gly-NH2 in triethylamine-containing 2-propanol was studied.Maximum yield of dipeptide Ac-Tyr-Gly-NH2 was obtained in 2-propanol with 2percent of water.Lower water content retards the reaction.Although higher water content accelerates the process, the yield of the dipeptide is reduced by enzymatically catalyzed hydrolysis of Ac-Tyr-OEt.The studied reaction proceeds analogously also in other aliphatic alcohols with low content of water except in methanol; it does not take place in dimethylformamide or dimethyl sulfoxide containing 2percent or 20percent of water.In 2-propanol with 2percent or 5percent of water, syntheses of the protected amino-terminal oxytocine and vasopressin tripeptide as well as other model peptides, were studied.In all the described experimetns, α-chymotrypsin without any stabilization or immobilization was employed.
- Cerovsky, Vaclav,Martinek, Karel
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p. 266 - 276
(2007/10/02)
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- Optically active 3,4-bis-(diphenylphosphino)-pyrrolidine, and rhodium complexes, containing it as chiral ligands
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There are described new optically active 3,4-bis-(diphenylphosphino)-pyrrolidines of the formula STR1 wherein Ph is a phenyl group and R is hydrogen, an alkyl group, an arylalkyl group or an acyl group, rhodium complexes containing a compound of formula (I) as its chiral ligands, said rhodium complexes having the formula where (en)2 is two molecules of a monoolefin or one molecule of a diolefin, A is an optically active compound of formula (I) and X- is a tetrafluoroborate, hexafluorophosphate or a perchlorate ion, and use of the rhodium complexes as catalysts for the homogeneous asymmetric hydrogenation of unsubstituted or β-substituted α-acylamino-acrylic acids.
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- Enantioselective Catalysis, 4. Synthesis of N-Substituted (R,R)-3,4-Bis(diphenylphosphino)pyrrolidines. The Use of their Rhodium Complexes for the Asymmetric Hydrogenation of α-(Acylamino)acrylic Acid Derivatives
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A simple synthesis of (R,R)-3,4-bis(diphenylphosphino)pyrrolidine (6a) and some N-substituted derivatives 6b-m is described. 6l and 6m are optically active tetraphosphanes, composed of two (R,R)-3,4-bis(diphenylphosphino)pyrrolidine units and a dicarboxylic residue.The structure of the parent compound 6a was determined by X-ray diffraction.From the phosphanes 6a-m the cationic 1,5-cyclooctadiene-bisphosphane-rhodium complexes 7a-m were prepared.The complexes 7l and 7m are ligand bridged bis(rhodium) dications.The complexes 7a-m were used for the asymmetric catalytic hydrogenation of the α-(acylamino)acrylic acid derivatives 9a-l.Enantiomeric excesses up to 100percent were achieved.Between 1 and 70 at the optical yields do not depend on the hydrogen pressure.The substrate/catalyst ratio can be as high as 50000/1.
- Nagel, Ulrich,Kinzel, Elke,Andrade, Juan,Prescher, Guenter
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p. 3326 - 3343
(2007/10/02)
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- Serine-Protease-Assisted Synthesis of Peptide Substrates for α-Chymotripsin
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δ-Chymotrypsin catalyzes peptide-bond formation between acylated amino-acid and peptide esters as the carboxyl component and amino-acid and peptide amides as the amino component.The conditions under which enzyme-catalyzed coupling can be used for fragment condensation in peptide synthesis is investigated.To illustrate the method the synthesis of tetra-, penta and hexapeptides of the structure Ac-Lxn-...-Lxl-Lyl-...-Lym-NH2 with Lxl = Tyr, designed as substrates for α-chymotrypsin is described.
- Bizzozero, Spartaco A.,Rovagnati, Bruno A.,Dutler, Hans
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p. 1707 - 1719
(2007/10/02)
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- Transition-Metal-Catalyzed Asymmetric Organic Synthesis via Polymer-Attached Optically Active Phosphine Ligands. 5. Preparation of Amino Acids in High Optical Yield via Catalytic Hydrogenation
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Two new optically active phosphinopyrrolidine monomers were prepared by the reaction of (2S,4S)-4-(diphenylphosphino)-2-pyrrolidine and (2R,4R)-4-(diphenylphosphino)-2-pyrrolidine with acryloyl chloride to give N-acryloyl-(2S,4S)-4-(diphenylphosphino)-2-pyrrolidine (1) and N-acryloyl-(2R,4R)-4-(diphenylphosphino)-2-pyrrolidine (2).Copolymerization of 1 and 2 with hydrophilic comonomers and a divinyl monomer provided cross-linked insoluble polymers containing 3-5percentof 1 or 2 that would swell in polar solvents.Exchange of rhodium (I) onto the polymer gave catalysts which were active for the asymmetric hydrogenation of N-acyl α-amino acids in high optical yields, the phosphine derived from the enantiomer of the naturally occurring 4-hydroxyproline giving (S)-amino acids.The catalysts could be reused with no loss in selectivity by simple filtration.
- Baker, Gregory L.,Fritschel, Scott J.,Stille, John R.,Stille, John K.
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p. 2954 - 2960
(2007/10/02)
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- Asymmetric Synthesis. Asymmetric Catalytic Hydrogenation Using Chiral Chelating Six-Membered Ring Diphosphines
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Rhodium(I) catalysts formed by the two chiral chelating six-membered ring diphosphines, 2,4-bis(diphenylphosphino)pentane (skewphos) and 1,3-bis(diphenylphosphino)butane (chairphos), are efficient catalysts for the hydrogenation of amino acid precursors.The two chiral phosphines differ in that skewphos probably adopts a chiral conformation whereas chairphos probably adopts an achiral conformation.This comparison evidences the importance of ring conformations in determining optical yields.The mechanism of asymmetric hydrogenation is discussed, and a number of particular and general conclusions are drawn which may prove useful in predicting optical yields from asymmetric synthesis.
- MacNeil, Patricia A.,Roberts, Nicholas K.,Bosnich, B.
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p. 2273 - 2280
(2007/10/02)
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- A New Chiral Rhodium(I) Complex of (2R,3R)-2,3-Bis(diphenylphosphino)butane for Asymmetric Hydrogenations
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Rhodium(I) complexes of the new chiral ligand (2R,3R)-2,3-bis(diphenylphosphino)butane (4) - which is easily prepared from natural tartaric acid - hydrogenate α-(acylamino)acrylic acids to natural (S)-acylamino acids in high chemical (95-100percent) and optical (80-100percent) yields.
- Koettner, Johann,Greber, Gerd
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p. 2323 - 2325
(2007/10/02)
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- Effects of organic solvents on immobilized enzyme catalyses. Chymotrypsin immobilized on Sephadex
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The esterolytic activities of native chymotrypsin (CT) and immobilized CT-Sephadex have been studied in the presence of up to 20 percent of the organic solvents methanol, ethanol, 2-propanol, tert-butyl alcohol, dioxane, or DMSO.The general cosolvent-induced inhibition of the native enzyme was attenuated for immobilized CT.Most noticeably, the apparent catalytic rate constants for the CT-Sephadex-catalyzed hydrolysis of N-acetyl-L-tyrosine ethyl ester were invariant over the 2-20 percent dioxane concentration range surveyed.In contrast, the activity of the native enzyme in 20 percent dioxane was only 3 percent the activity recorded in the absence of cosolvent.Increasing the hydrophobic character of the protic cosolvents destabilized the native enzyme but stabilized CT-Sephadex.Both native and immobilized CT displayed remarkable stability in 20 percent aqueous DMSO (t1/2 > 200 days).At least part of the DMSO-induced inhibition of native CT and CT-Sephadex was offset by increasing the apparent pH of the reaction medium.The altered kinetic patterns for CT-Sephadex are best explained by the effects of diffusional limitations on the apparent enzyme activity.The best compromise solvent for preparative applications of CT-Sephadex was found to be tert-butyl alcohol.
- Pliura, Diana H.,Jones, J. Bryan
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p. 2633 - 2640
(2007/10/02)
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