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Transamidation and Decarbonylation of N-Phthaloyl-Amino Acid Amides Enabled by Palladium-Catalyzed Selective C–N Bond Cleavage
Amides are important functional synthons that have been widely used in the construction of peptides, natural products, and drugs. The C–N bond cleavage provides the direct method for amide conversion. However, amides, especially secondary amides, tend to
Zhang, Hao-Yu,Tao, Xuan-Wen,Yi, Li-Na,Zhao, Zhi-Gang,Yang, Qiang
p. 231 - 242
(2022/01/11)

Green Esterification of Carboxylic Acids Promoted by tert-Butyl Nitrite
In this work, the green esterification of carboxylic acids promoted by tert-butyl nitrite has been well developed. This transformation is compatible with a broad range of substrates and exhibits excellent functional group tolerance. Various drugs and substituted amino acids are applicable to this reaction under near neutral conditions, with good to excellent yields.
Cheng, Xionglve,Jiang, Gangzhong,Li, Xingxing,Tao, Suyan,Wan, Xiaobing,Zhao, Yanwei,Zheng, Yonggao
supporting information
p. 2713 - 2718
(2021/06/25)

Amide Synthesis by Nickel/Photoredox-Catalyzed Direct Carbamoylation of (Hetero)Aryl Bromides
Herein, we report a one-electron strategy for catalytic amide synthesis that enables the direct carbamoylation of (hetero)aryl bromides. This radical cross-coupling approach, which is based on the combination of nickel and photoredox catalysis, proceeds at ambient temperature and uses readily available dihydropyridines as precursors of carbamoyl radicals. The method's mild reaction conditions make it tolerant of sensitive-functional-group-containing substrates and allow the installation of an amide scaffold within biologically relevant heterocycles. In addition, we installed amide functionalities bearing electron-poor and sterically hindered amine moieties, which would be difficult to prepare with classical dehydrative condensation methods.
Alandini, Nurtalya,Buzzetti, Luca,Candish, Lisa,Collins, Karl D.,Favi, Gianfranco,Melchiorre, Paolo,Schulte, Tim
supporting information
p. 5248 - 5253
(2020/03/03)

Electrochemical anion pool synthesis of amides with concurrent benzyl ester synthesis
An electrosynthesis method for amide bond formation has been developed in an attempt to increase the atom economy for this class of reactions. This "anion pool" method electrochemically generates strong nucleophiles from amine substrates. The amine nucleophiles then react with acid anhydrides to generate amides, and the by-product from this reaction undergoes further chemical transformations to generate pharmaceutically relevant benzoic esters. These one-pot reactions are operationally simple, are performed at room temperature, and avoid rare transition metals and added bases. The amide synthesis is amenable to primary and secondary amines and a variety of anhydrides with yields up to 90% obtained. Atom economy and process mass index (PMI) values calculated for this procedure indicate that this process can be considered greener compared to traditional amide synthesis routes used by industry. Furthermore, this electrochemical approach showed unique selectivity when substrates that contained two inequivalent amine moieties were examined.
Mevan Dissanayake,Melville, Alex D.,Vannucci, Aaron K.
supporting information
p. 3165 - 3171
(2019/06/18)

Microwave-Assisted Ruthenium-Catalysed ortho-C?H Functionalization of N-Benzoyl α-Amino Ester Derivatives
A microwave-assisted highly efficient intermolecular C?H functionalization sequence has been developed to access substituted isoquinolones using α-amino acid esters as a directing group. This methodology enables a wide range of N-benzoyl α-amino ester derivatives to react via a Ru-catalysed C?H bond activation sequence, to form isoquinolones with moderate to excellent yields. As an additional advantage, our strategy proved to be widely applicable and also enabled the reaction of alkenes to provide access to alkenylated benzamides. The methodology was also extended towards the synthesis of isoquinoline alkaloids derivatives viz. oxyavicine and a dipeptide. The developed protocol is simple and cheap, avoids tedious workup procedures and works efficiently under MW irradiation. (Figure presented.).
Sharma, Nandini,Bahadur, Vijay,Sharma, Upendra K.,Saha, Debasmita,Li, Zhenghua,Kumar, Yogesh,Colaers, Jona,Singh, Brajendra K,Van der Eycken, Erik V.
supporting information
p. 3083 - 3089
(2018/08/24)

Formation of Non-Natural α,α-Disubstituted Amino Esters via Catalytic Michael Addition
The enolate monoanion of amino esters is explored, and the first catalytic Michael addition of α-amino esters is demonstrated. These studies indicate that the acidity of the αC-H is the primary factor determining reactivity. Thus, polyfluorophenylglycine amino esters yield novel α-amino esters in the presence of a catalytic amount of a guanidine-derived base and Michael acceptors. Reactivity requires an acidic N-H, which is accomplished using common protecting groups such as N-Bz, N-Boc, and N-Cbz. Calculations and labeling experiments provide insight into the governing principles in which a key C-to-N proton transfer occurs, resulting in an expansion of the scope to include a number of natural amino esters. The study culminates with a late-stage functionalization of peptidic γ-secretase inhibitor, DAPT.
Teegardin, Kip A.,Gotcher, Lacey,Weaver, Jimmie D.
supporting information
p. 7239 - 7244
(2018/11/25)

Synthesis of Hydrazones from Amino Acids and their Antimicrobial and Cytotoxic Activities
Hydrazones 6a–6n were synthesized from different amino acids with various aldehydes under reflux in methanol/ethanol. The structures of synthesized compounds were ascertained by elemental analysis and spectroscopic techniques. A comparative study of the antimicrobial activity and cytotoxicity was carried out of the N-protected amino acids, their esters, hydrazides, and the respective hydrazones, providing good results in cytotoxicity studies.
Abid, Obaid-Ur-Rahman,Khatoon, Ghamama,Arfan, Muhammad,Sajid, Imran,Langer, Peter,Rehman, Wajid,Rahim, Fazal,Yasir, Muhammad,Waqar, Muhammad,Haleem, Kashif Syed
p. 1079 - 1087
(2017/09/26)

Regiodivergent Enantioselective γ-Additions of Oxazolones to 2,3-Butadienoates Catalyzed by Phosphines: Synthesis of α,α-Disubstituted α-Amino Acids and N,O-Acetal Derivatives
Phosphine-catalyzed regiodivergent enantioselective C-2- and C-4-selective γ-additions of oxazolones to 2,3-butadienoates have been developed. The C-4-selective γ-addition of oxazolones occurred in a highly enantioselective manner when 2-aryl-4-alkyloxazol-5-(4H)-ones were employed as pronucleophiles. With the employment of 2-alkyl-4-aryloxazol-5-(4H)-ones as the donor, C-2-selective γ-addition of oxazolones took place in a highly enantioselective manner. The C-4-selective adducts provided rapid access to optically enriched α,α-disubstituted α-amino acid derivatives, and the C-2-selective products led to facile synthesis of chiral N,O-acetals and γ-lactols. Theoretical studies via DFT calculations suggested that the origin of the observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic oxazolide and the electrophilic phosphonium intermediate.
Wang, Tianli,Yu, Zhaoyuan,Hoon, Ding Long,Phee, Claire Yan,Lan, Yu,Lu, Yixin
p. 265 - 271
(2016/01/25)

Light-enabled synthesis of anhydrides and amides
Recently, we have demonstrated that the photogeneration of Vilsmeier-Haack reagents is possible using only dimethylformamide (DMF) and tetrabromomethane (CBr4) in the bromination of alcohols. Extending these findings to carboxylic acid substrates has produced a mild and facile approach to the in situ formation of symmetric anhydrides, which were conveniently converted to amide derivatives in a one-pot process. The efficient protocols discussed herein are marked by use of UVA LEDs (365 nm), which have reduced the reaction times and come with a low setup cost.
Mccallum, Terry,Barriault, Louis
p. 2874 - 2878
(2015/03/30)

N-heterocyclic carbene-catalyzed oxidative amidation of aldehydes with amines
The N-heterocyclic carbene (NHC)-catalyzed oxidative amidation of aromatic aldehydes with amines in the presence of N-bromosuccinimide (NBS) as an oxidant has been developed for the synthesis of amides. This amidation strategy is tolerant to both the electronic and the steric nature of the aryl aldehydes employed. The present methodology was extended to chiral amino acid derivatives to generate the corresponding amides in good yields and excellent ee values (>98%).
Alanthadka, Anitha,Maheswari, C. Uma
supporting information
p. 1199 - 1203
(2015/04/22)

Kinetic resolution of unsaturated amides in a chlorocyclization reaction: Concomitant enantiomer differentiation and face selective alkene chlorination by a single catalyst
The first example of a kinetic resolution via chlorofunctionalization of olefins is reported. The enantiomers of racemic unsaturated amides were found to have different hydrogen-bonding affinities for chiral Lewis bases in numerous solvents. This interaction was exploited in developing a kinetic resolution of racemic unsaturated amides via halocyclization. The same catalyst serves to both sense chirality in the substrate as well as mediate a highly face-selective chlorine delivery onto the olefin functionality, resulting in stereotriad products in up to 99:1 dr and up to 98.5:1.5 er. The selectivity factors were typically greater than 50 to allow for the simultaneous synthesis of both the products and unreacted substrates in highly enantioenriched form at yields approaching 50%. The reaction employs catalytic amounts (≤0.50 mol %) of a commercially available and recyclable organocatalyst.
Jaganathan, Arvind,Staples, Richard J.,Borhan, Babak
p. 14806 - 14813
(2013/10/22)

Synthesis and antitumor evaluation of some 1,3,4-oxadiazole-2(3H)-thione and 1,2,4-triazole-5(1H)-thione derivatives
A series of 1,3,4-oxadiazole-2-thione and 1,2,4-triazole-5-thione derivatives have been successfully synthesized and studied for their antitumor activity. These compounds were prepared from carboxylic acids and chiral aminoacid esters. The prepared compounds were evaluated for their cytotoxicity against cancer in vitro using hydroxyurea (HU) as positive control. A fair number of compounds were found to have significant antitumor activity. To study the molecular basis of interaction and affinity of binding of the target molecules, all the compounds were docked into the ATPase domain of TP-II and tubulin using Schroedinger. Springer Science+Business Media, LLC 2010.
Feng, Cheng Tao,Wang, Ling Dong,Yan, Yu Gang,Liu, Jian,Li, Shao Hua
experimental part
p. 315 - 320
(2012/09/07)

Synergistic chiral ion pair catalysts for asymmetric catalytic synthesis of quaternary α,β-diamino acids
The combination of a chiral phosphate anion with a silver ion has been demonstrated as a powerful and synergistic ion pair catalyst for the aza-Mannich reaction. A series of valuable quaternary α,β-diamino acid derivatives was obtained in high yield, and with excellent diastereo- (up to 25:1 dr) and enantioselectivity (up to 99% ee). The adducts can be smoothly transformed into the corresponding protected chiral quaternary α,β-diamino acids by a one-pot hydrolysis reaction.
Shi, Shi-Hui,Huang, Fu-Ping,Zhu, Ping,Dong, Zhen-Wen,Hui, Xin-Ping
scheme or table
p. 2010 - 2013
(2012/06/01)

Benzotetramisole-catalyzed dynamic kinetic resolution of azlactones
(Figure Presented) Enantioselective acyl transfer catalyst benzotetramisole (BTM) has been found to promote dynamic kinetic resolution of azlactones providing di(1-naphthyl)methyl esters of α-amino acids with up to 96% ee.
Yang, Xing,Lu, Guojian,Birman, Vladimir B.
scheme or table
p. 892 - 895
(2010/04/29)

Oxidative amidation of aldehydes and alcohols with primary amines catalyzed by KI-TBHP
Oxidative amidation of aldehydes and alcohols with amines to afford the corresponding amides in excellent yields and ee values over 98% is achieved by using a catalytic amount of KI in combination with TBHP as the external oxidant. This method avoids the use of expensive and/or air-sensitive reagents. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Rajender Reddy,Uma Maheswari,Venkateshwar,Lakshmi Kantam
supporting information; experimental part
p. 3619 - 3622
(2009/05/07)

Asymmetric electrochemical oxidation of 1,2-diols, aminoalcohols, and?aminoaldehydes in the presence of chiral copper catalyst
Asymmetric oxidation of 1,2-diols, aminoalcohols, and aminoaldehydes in the presence of copper(II) triflate and (R,R)-Ph-BOX was accomplished by electrochemical method using Br- as a mediator. This oxidation was applicable to kinetic resolution of racemic cis-cycloalkane-1,2-diols, aminoalcohols, and aminoaldehydes to afford optically active compounds with good to high enantioselectivity.
Minato, Daishirou,Arimoto, Hitomi,Nagasue, Yoko,Demizu, Yosuke,Onomura, Osamu
p. 6675 - 6683
(2008/12/20)

New pseudonucleosides containing chiral oxazolidin-2-ones and Cyclosulfamides as aglycones: Synthesis and antiviral evaluation
A series of chiral cyclosulfamides and oxazolidinon-2-ones have been synthesized starting from aminoacids. Regioselective substitution of these pseudopyrimidic heterocyles was carried out under Mitsunobu conditions. Best substitution results were obtained by preliminary deprotection of cyclosulfamides and their condensation with β -D-ribofuranose. Chiral oxazolidin-2-ones were coupled directly with D-ribofuranose. All compounds were tested against HSV-2, VV and SV viruses. Two compounds 6b and 6e showed significant activities against HSV-type 1. Copyright Taylor & Francis Group, LLC.
Bouleghlem, Hocine,Berredjem, Malika,Lecouvey, Marc,Aouf, Nour-Eddine
p. 1539 - 1542
(2008/09/20)

Rate constants for 1,n-hydrogen transfer reactions in some amino acid derived radicals
Absolute rate constants for 1,n-hydrogen atom transfers in some substituted amino acid derived radicals have been determined in benzene through the use of competitive kinetic experiments. Radicals derived from methyl N-(2-iodobenzoyl)-N-(tert-butyloxycarbonyl)glycinate, -alaninate, -leucinate, -tert-leucinate and -phenylglycinate undergo intramolecular 1,5-hydrogen atom transfer to afford the corresponding α-amino acid ester radicals with rate constants in the range: 1.0-4.3 × 107 s-1 at 80 °C. Where abstractable hydrogen atoms exist in the amino acid side-chain, 1,6- and 1,7-translocations are competitive processes.
Zeng, Le,Kaoudi, Talbi,Schiesser, Carl H.
p. 7911 - 7914
(2007/10/03)

Homogeneous catalytic aminocarbonylation of iodoalkenes and iodobenzene with amino acid esters under conventional conditions and in ionic liquids
Amino acid methyl esters were used as amine nucleophiles in palladium catalysed aminocarbonylation of iodobenzene and iodoalkenes (1-iodo-cyclohexene and 17-iodo-androst-16-ene). 2-Oxo-carboxamide type derivatives can be isolated as a result of double CO insertion by using iodobenzene as a substrate at elevated carbon monoxide pressure. On the contrary, carboxamides of expected structure were obtained exclusively in excellent yields in the whole pressure range by using iodoalkenes. The aminocarbonylation of 17-iodo-androst-16-ene in [bmim][PF6] or [bmim][BF4] (where bmim=1-butyl-3-methyl- imidazolium cation) ionic liquids was also carried out and the ionic liquid-catalyst mixtures have been reused several times with only a small loss of activity.
Müller, Erno,Péczely, Gábor,Skoda-F?ldes, Rita,Takács, Eszter,Kokotos, George,Bellis, Evagelos,Kollár, László
p. 797 - 802
(2007/10/03)

Simple and Efficient Cleavage Reaction of the Boc Group in Heterocyclic Compounds
A series of chiral cyclosulfamides have been synthesized by alkaline cyclisation starting from N-benzoylamino acids (Ala, Val, Leu, Phe) derivatives and chlorosulfonyl isocyanate. A simplified and regioselective deprotection of the cyclic compounds (cyclosulfamides) containing the tert-butyloxycarbonyl group (Boc) has been achieved in good yield by fusion under reduced pressure.
Nadia, Klai,Malika, Berredjem,Nawel, Khettache,MedYazid, Belghit,Zine, Regainia,Aouf, Nour-Eddine
p. 57 - 60
(2007/10/03)

Ceric(IV) ammonium nitrate mediated transesterification and esterification
The transesterification of carboxylic esters and the esterification of carboxylic acids are effected under mild conditions in the presence of ceric(IV) ammonium nitrate (CAN).
Stefane, Bogdan,Kocevar, Marijan,Polanc, Slovenko
p. 1703 - 1707
(2007/10/03)

Solid-phase synthesis of monocyclic β-lactam derivatives
Liquid-phase studies concerning the solid-phase synthesis of monocyclic β-lactams via the esterenolate imine condensation route have been conducted utilizing triazene esters 1 and 2 as model compounds. Esters were attached to benzylamine resin 6 by a triazene linker employing the respective diazonium salts. Immobilized ester-enolates 8 and 10 were reacted with various imines and imine precursors to give polymer-bound β-lactams 14 and 17 in different substitution patterns. Traceless cleavage from the triazene linker yields the desired β-lactams 16 and 19.
Schunk,Enders
p. 8034 - 8042
(2007/10/03)

A photochemical approach to phenylalanines and related compounds by alkylation of glycine
Phenylalanines can be prepared on UV photolysis of protected glycines in the presence of di-tert-butyl peroxide, substituted toluenes and the photosensitiser benzophenone. These reactions, which lead to highly selective mono-alkylation at the α-position of glycines, involve coupling of captodative α-glycine radicals with benzyl radicals. This method can be used to selectively alkylate a variety of glycine derivatives using a range of substituted toluenes under neutral reaction conditions.
Knowles, Haydn S.,Hunt, Keith,Parsons, Andrew F.
p. 8115 - 8124
(2007/10/03)

Efficient one-pot formation of amides from benzyl carbamates: Application to solid-phase synthesis
A convenient one-pot protocol for the conversion of benzyl carbamates to amides is described. The general applicability of the procedure is illustrated using various types of substrates. This new method proceeds rapidly under mild conditions, in good yields, and without noticeable racemization. This protocol was applied to solid-phase synthesis to prepare amides and esters from Merrifield resin-bound carbamates and carbonates. (C) 2000 Elsevier Science Ltd.
Li, Wen-Ren,Yo, Ying-Chih,Lin, Yu-Sheng
p. 8867 - 8875
(2007/10/03)

Molecular recognition on crystallization of enantiopure and racemic N-benzoylalanine methyl ester
The melting points of crystals of (S)- and (RS)-N-benzoylalanine methyl ester derived from solutions of ethyl acetate/light petroleum are 56-57.5° and 81.5-82.5°, respectively, reflecting differences in lattice energy that are apparent from the crystal structures. A more extensive mode of association between chains, uniformly stabilized by N-H?O=C interactions, is found in the racemate leading to a more efficient packing of molecules. The higher lattice energy of the racemate has been confirmed through the enantiomeric enrichment of an optically active sample and the partial resolution of (RS)-N-benzoyl(2-2H)alanine methyl ester, through molecular recognition on crystallization. CSIRO 2000.
Coghlan, Daniel R.,Easton, Christopher J.,Tiekink, Edward R. T.
p. 551 - 556
(2007/10/03)

A facile synthesis of amides from 9-fluorenylmethyl carbamates and acid derivatives
A mild and convenient one-pot procedure for the synthesis of amides from 9-fluorenylmethyl carbamates and acids using potassium fluoride, triethylamine and various coupling reagents in DMF at room temperature is described. The scope of this procedure was also tested in the coupling of a variety of 9-fluorenylmethyloxycarbonyl-protected amines with active moieties such as anhydrides, acyl imidazolides, activated esters, tosyl chlorides, and acyl halides.
Li, Wen-Ren,Chou, Hsueh-Hsuan
p. 84 - 90
(2007/10/03)

Synthesis of 1,2,5-thiadiazolidines 1,1-dioxides (Cyclosulfamides) starting from amino acids and chlorosulfonyl isocyanate
We report here a practical access to a series of five-membered cyclosulfamides (1,2,5-thiadiazolidines 1,1-dioxides) N2 substituted by the BOC group. These compounds are synthesized starting from chlorosulfonyl isocyanate and nitrogen mustards or amino acids. The derivatization of amino acids can lead to an alkyl group on C-4 with a well-defined configuration; in this case the N5 position was protected by a benzyl group. These compounds are valuable tools for asymmetric synthesis. (C) 2000 Elsevier Science Ltd.
Rega?nia, Zine,Abdaoui, Mohamed,Aouf, Nour-Eddine,Dewynter, Georges,Montero, Jean-Louis
p. 381 - 387
(2007/10/03)

Photochemical alkylation of glycine leading to phenylalanines
UV photolysis of protected glycines in the presence of di-tert-butyl peroxide, benzophenone and substituted toluenes is shown to lead to selective alkylation at the α-position. Phenylalanines are isolated in yields of generally > 50% (based on recovered s
Knowles,Hunt,Parsons
p. 7121 - 7124
(2007/10/03)

Solid-phase synthesis of beta-lactams via the ester enolate-imine condensation route.
The ester enolate-imine condensation route to beta-lactams via an immobilized ester enolate has been achieved for the first time. The key reaction in the synthesis is the cyclization of the resin bound ester dianion and an imine. Traceless cleavage from the T1-triazene linker system yields the desired beta-lactams.
Schunk,Enders
p. 907 - 910
(2007/10/03)

Enantioselective enolate protonation: Matching chiral aniline and substrate acidity
A comparison of chiral anilines 1a-f in the asymmetric protonation of enolate 15 shows that the optimum ΔpK(a) value (chiral acid vs protonated enolate) for the highest enantioselectivity is ca. 3 (Table 2). An extension of this concept to amino acid enolates was possible, and 1e was found to give the best enantioselectivity (85% ee) with the alanine-derived N-lithioenolate 5a (Table 3). Changes in aniline pK(a) due to variation of substituents at the aniline nitrogen were evaluated briefly, but these changes did not show consistent trends in the enantioselectivity vs pK(a).
Vedejs,Kruger,Suna
p. 7863 - 7870
(2007/10/03)

Hydro-de-phosphoniation of 4-substituted-4-triphenylphosphonio-5(4H)-oxazolones with hydrogen iodide
4-Substituted-4-triphenylphosphonio-5(4H)-oxazolones, when reacted with hydrogen iodide in methylene chloride at room temperature, undergo hydro-de-phosphoniation to 5(4H)-oxazolonium salts, which react with methanol and triethylamine to give the correspo
Mazurkiewicz, Roman,Pierwocha, Anna W.,Zabska, Agata
p. 167 - 178
(2007/10/03)

Dynamic Kinetic Resolutions Catalyzed by a Planar-Chiral Derivative of DMAP: Enantioselective Synthesis of Protected α-Amino Acids from Racemic Azlactones
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Liang, Jack,Ruble, Craig,Fu, Gregory C.
p. 3154 - 3155
(2007/10/03)

Nitrate esters in the generation of amino acid radicals
Nitrate esters, prepared by treatment of β-hydroxy-α-amino acid derivatives with nitric acid, react with tributyltin hydride to give the corresponding alkoxyl radicals. These radicals readily undergo β-scission, providing a convenient route for the regiocontrolled production of α-carbon-centred amino acid radicals. By examining the partitioning of the alkoxyl radicals between the β-scission process and the competing hydrogen transfer reaction, it has been possible to evaluate the influence of electronic and steric effects on the β-scission reaction and the formation of the carbon-centred radicals.
Easton, Christopher J.,Ivory, Andrew J.,Smith, Craig A.
p. 503 - 507
(2007/10/03)

Asymmetric synthesis of uncommon α-amino acids by diastereoselective alkylations of a chiral glycine equivalent
For the purpose of practical preparations of a variety of enantiomerically pure uncommon α-amino acids, alkylations of the chiral glycine equivalent 5, which possesses axially chiral binaphthol as an auxiliary, with several electrophiles were investigated. The alkylation proceeded smoothly in satisfactory chemical yield with high diastereo-selectivities to give protected α-amino acid derivatives. The free hydroxyl group of the auxiliary played an important role for the induction of diastereoselectivity. Using (S)-1,1'-binaphthalene-2,2'-diol as a chiral auxiliary, D-α-amino acid derivatives having the unnatural (R)-configuration were predominantly obtained. Some of the alkylated products were converted into free non- proteinogenic D-α-amino acids.
Tanaka, Kiyoshi,Ahn, Mija,Watanabe, Yukari,Fuji, Kaoru
p. 1771 - 1782
(2007/10/03)

Single-step enzymatic conversion of peptide amides to esters
It is shown that the C-terminal amide groups in N-protected peptides could be efficiently replaced by ester groups via kinetically-controlled papain-catalyzed acyl transfer reactions in aqueous methanol. The specificity of papain was substantially shifted towards the cleavage of C-terminal amide bond in dipeptide substrates by methanol, thus suppressing undesired peptide bond cleavage during esterification.
Meos, Helle,Haga, Mati,Tougu, Vello
p. 2343 - 2346
(2007/10/02)

Research on antiviral agents. 4. Studies on the chemistry of 6-methyl-2-methoxy-4-O-acyloxy and 6-methyl-2,4-di-O-acyloxypyrimidine derivatives as new acylation reagents and inhibitors of uracil DNA glycosylases.
The synthesis of 6-methyl-2-methoxy-4-O-acyloxy and 6-methyl-2,4-di-O-acyloxypyrimidine derivatives 2 and 5 along with their properties as acylating agents of amines, alcohols, thiols and α-amino acids have been reported. Interestingly some of the title products revealed an inhibitory activity against the human and herpetic DNA glycosylases.
Botta,Saladino,Gentile,Summa,Nicoletti,Verri,Focher,Spadari
p. 3603 - 3618
(2007/10/02)

Enzymatic Asymmetric Synthesis of α-Amino Acids. Enantioselective Cleavage of 4-Substituted Oxazolin-5-ones and Thiazolin-5-ones
A general enzymatic asymmetric synthesis of L-α-amino acids has been developed.This method entails the use of the Pseudomonas cepacia lipase (P-30) to catalyze the enantioselective methanolysis of a variety of 4-substituted 2-phenyloxazolin-5-one derivatives in a nonpolar organic solvent to furnish optically active N-benzoyl-L-α-amino acid methyl esters (ee = 66-98 percent), which in turn is subjected to a protease-catalyzed kinetic resolution yielding enantiomerically pure N-benzoyl-L-α-amino acids.This synergistic coupling of two enzymes allows the ready preparation of L-α-amino acids of high enantiopurity in yields greater than 50 percent, an inherent advantage over conventional resolution procedures.Two proteases were found to catalyze the enantioselective hydrolysis of a variety of 4-substituted 2-phenylthiazolin-5-one derivatives to give N-(thiobenzoyl)-L-α-amino acids of high optical purity.
Crich, Joyce Z.,Brieva, Rosario,Marquart, Peer,Gu, Rui-Lin,Flemming, Steffen,Sih, Charles J.
p. 3252 - 3258
(2007/10/02)

The asymmetric synthesis of α-amino acids via the addition of grignard reagents to imine derivatives
The ester-8-phenylmenthyl N-Boc-glycinate 5a, undergoes free radical bromination by N-bromosuccinimide to give 8-phenylmenthyl N-Boc-bromoglycinate 8. Treatment of the bromide 8 with a variety of Grignard reagents at low temperature gave 8-phenylmenthyl (S-N-Boc-2-alkylgrycinates with high diastereoselectivity. Conditions were found for the hydrolysis of these derivatives with no racemization of the resultant amino acid.
Hamon, David P. G.,Massy-Westropp, Ralph A.,Razzino, Pasquale
p. 5163 - 5178
(2007/10/02)

The effect of base and additive on the alkylation of methyl hippurate
Contrary to a published report, C-alkylation of methyl hippurate requires two equivalents of base. The choice of additive (TMEDA or HMPA) influences the result. Deuteration of the enolate gives results which depend on both the deuterium source and the nature of the additive.
McIntosh,Thangarasa,Ager,Zhi
p. 6219 - 6224
(2007/10/02)

A New Method for the α-Vinylation of Protected α-Amino Acids; Ethylene Oxide as Vinyl Cation Equivalent
A convenient and conceptually new strategy for the transformation of α-amino acids into the corresponding α-vinyl amino acids is described; commercially available ethylene oxide serves as a vinyl cation equivalent.
Berkowitz, David B.
p. 1819 - 1829
(2007/10/02)

INDIRECT ELECTROCHEMICAL α-METHOXYLATION OF N-ACYL AND N-CARBOALKOXY α-AMINO ACID ESTERS AND APPLICATION AS CATIONIC GLYCINE EQUIVALENTS
Indirect electrochemical methoxylation of N-acyl and N-carboalkoxy α-amino acid esters in α-position to nitrogen is possible, if chloride is used as mediator.The course of the reaction depends upon the protecting group as well as upon the amino acid side-chain.Increased electron withdrawing effects of the protecting group are accelerating the reaction.On the other hand aliphatic side-chains are diminishing the reactivity.High chloride ion concentrations improve the current yields surprisingly strong.
Ginzel, Klaus-Dieter,Brungs, Peter,Steckhan, Eberhard
p. 1691 - 1702
(2007/10/02)

Selective Reaction of Glycine Residues in Hydrogen Atom Transfer from Amino Acid Derivatives
Relative rates of reaction of the N-benzoylamino acid methyl esters 1a-4a with N-bromosuccinimide and of 1a-4a with di-tert-butyl peroxide are reported.The selective reaction of glycine derivatives in these and other reactions of N-acylamino acid derivatives is attributed to the relative stability of intermediate radicals produced by hydrogen atom transfer.Radicals formed by hydrogen abstraction from N-acylglycine derivatives may adopt planar conformations which are relatively free of nonbonding interactions and in which there is maximum delocalization of the unpairedelectron, whereas radicals produced by similar reactions of derivatives of other amino acids are relatively unstable because of nonbonding interactions.In accord with this hypothesis, methyl pyroglutamate (5a) reacts at a faster rate than N-benzoylglycine methyl ester (1a) in reactions with either N-bromosuccinimide or di-tert-butyl peroxide.Anomalous rates of reaction of N-benzoylproline methyl ester (6a) are rationalized in terms of the regioselectivity of hydrogen atom transfer.Evidence for the mechanisms of reactions of 1a-6a is derived from product studies and by comparison of the relative rates of reactions of 1a-6a with those of the deuteriated amino acid derivatives 1b, 2b, 3b,c, 5b, and 6b,c.
Burgess, Vicky A.,Easton, Christopher J.,Hay, Michael P.
p. 1047 - 1052
(2007/10/02)

Dimerization of Glycine Derivatives
The bromide (5), prepared by treatment of the glycine derivative (4) with N-bromosuccinimide, reacted with hexabutylditin to give diastereoisomers of the glycine dimer (7), only when moisture was rigorously excluded from the reaction.Otherwise the major products were the diastereoisomers of the ether (11).The structure of the racemic diastereoisomer (11) was determined by X-ray crystallography.Photolysis of mixtures of the glycine derivative (4) and di-t-butyl peroxide gave the alanine derivative (10) in addition to the diastereoisomeric dimers (7).
Burgess, Vicky A.,Easton, Christopher J.,Hay, Michael P.,Steel, Peter J.
p. 701 - 710
(2007/10/02)

Studies on Diazepines. XXVIII. Syntheses of 5H-1,3-Diazepines and 2H-1,4-Diazepines from 3-Azidopyridines
Photolysis of 2-unsubstituted (5a-f) and 2,4-disubstituted (5k, l) 3-azidopyridines in the presence of sodium methoxide resulted in ring expansion to give the 4-methoxy-5H-1,3-diazepines (8 and 18), presumably via the azirine intermediates 6 and 17 derived from the initially formed singlet 3-pyridylnitrenes by cyclization at the 2-position of the pyridine ring.On the other hand, in the photolysis of 2-substituted 3-azidopyridines (5g-j), the cyclization of the nitrenes occurred predominantly at the vacant 4-position giving rise to the 3-methoxy-2H-1,4-diazepines (13).Keywords--3-azidopyridine; photolysis; pyridylnitrene; ring expansion; 5H-1,3-diazepine; 2H-1,4-diazepine; azirine intermediate
Sawanishi, Hiroyuki,Tajima, Kayoko,Tsuchiya, Takashi
p. 4101 - 4109
(2007/10/02)

Regio-selective diazepine formation from 3-azidopyridines: The first examples of monocyclic 2H-1,4-diazepines
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Sawanishi,Tsuchiya
p. 5603 - 5605
(2007/10/02)

AMIDOACETONE ENOLATE ANIONS: ALKYLATION AND MICHAEL REACTION
The lithyum enolate derived from benzamidoacetone (1) can be regiospecifically alkylated at C(1) and stereospecifically added in conjugate fashion to cyclohexenone without resorting to protection of free NH.Comparison is made with alkylations of methyl hippurate.
Hoye, Thomas R.,Duff, Steven R.,King, Rita S.
p. 3433 - 3436
(2007/10/02)

The Structure of a Toxic Octapeptide from the Larvae of Sawfly
The amino acid sequence of an octapeptide from sawfly (Lophyrotoma interrupta) larvae, which acts as a liver toxin, has been determined as C6H5COAla-Phe-Val-Ile-Asp-Asp-Glu-Gln.The amino acids, Ala, Phe, Asp5, and Glu7 residues, have the D absolute configuration.
Williams, Dudley H.,Santikarn, Sitthivet,Angelis, Francesco De,Smith, Richard J.,Reid, David G.,at al.
p. 1869 - 1878
(2007/10/02)

OXIDATION OF AMINO ACID ESTERS WITH ACYL PEROXIDES
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Milewska, Maria,Kolasa, Teodozyj,Chimiak, Andrzej
p. 2215 - 2218
(2007/10/02)

Mild Conversion of Carboxamides and Carboxylic Acid Hydrazides to Acids and Esters
A mild and selective conversion of unsubstituted carboxamides and carboxylic acid hydrazides to the corresponding acids and esters is brought about by the use of acidic resins.Application of the procedure to several carboxamides and carboxylic acid hydrazides is described.
Greenlee, William J.,Thorsett, Eugene D.
p. 5351 - 5353
(2007/10/02)

Von der basenkatalysierten Ringoeffnung von 2H-Azirinen zu einer α-Alkylierungsmethode von primaeren Aminen
It is shown than fluorene-9'-spiro-2-(3-phenyl-2H-azirine) (1) on treatment with various alcohols in the presence of the corresponding alkoxide ions yields N-(9'-fluorenyl)benzimidates 2a-d (Scheme 1). 2,2,3-Triphenyl-2H-aziridine (3) reacts with methanol in a similar manner (Scheme 2).Benzimidates 2a (Scheme 3), 8 (Scheme 4) and 10 (Scheme 5) can easily be deprotonated by butyllithium (BuLi) or lithium diisopropylamide (LDA) in tetrahydrofuran (THF) to 1-methoxy-2-aza-allylanions, that can be alkylated, at C(3), exclusively, by various electrophiles (e.g.R-X (X = I, Br), RCHO or methyl acrylate (see also Scheme 6)).As the acidic hydrolyses (1 N HCl) of benzimidates 9 and 11 leads to the corresponding α-alkylated free amines 15 and 18 (Scheme 7 and 8), benzoyl derivatives 16 and 19 are obtained from the hydrolysis under basic conditions.On the other hand it is observed that a catalyzed Chapman rearrangement of 9 and 11 results in the formation of N-benzoyl-N-methyl derivatives 17 and 20 (Scheme 7 and 8).The described reactions offer a simple method for the α-alkylation of actived primary amines.
Schulthess, Adrian Heinz,Hansen, Hans-Juergen
p. 1322 - 1336
(2007/10/02)