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The treatment of diethyl α,β‐dehydroaminophosphonate 1 with various arenes (ArH=toluene 2 a, benzene 2 b, anisole 2 c, bromobenzene 2 d, chlorobenzene 2 e, benzyl alcohol 2 f, p‐xylene 2 g) in acetic acid (AcOH) at 120 °C for 8 h in the presence of Pd(OAc)2 (10 % mol, OAc=acetate) and AgOAc (3.4 equivalents) results in the formation of the corresponding β‐aryl derivatives E‐Ar(H)C=C(NHAc)P(O)(OEt)23 a–3 g. The reaction proceeds through double C−H activation (arene and alkene) and subsequent C−C oxidative coupling (Fujiwara–Moritani reaction), processes catalyzed by Pd and assisted by Ag. The obtained products 3 a–3 g are isosteric analogs of phenylalanine and are obtained with high selectivity. Thus, geometrical E‐isomers have been obtained in all studied cases, however mixtures of ortho‐/meta‐/para‐isomers are observed when the activated position in the starting arene 2 is considered. [ABSTRACT FROM AUTHOR]

Within this work an efficient procedure for the synthesis of the vinyl phosphonate tripeptide dehydrophos is described. This procedure constitutes a significant improvement over previously described strategies, since critical transformations in the synthesis of dehydrophos were carried out in only two synthetic steps, with higher yields and under smooth conditions. Thus, the dehydrophosphoalanine residue was generated by means of the Horner–Wadsworth–Emmons reaction of formaldehyde with a peptide bearing an aminomethylbis(phosphonate) moiety, whereas deprotection of the N‐terminal position of the thus‐obtained dehydrophosphonopeptide and partial hydrolysis of the dimethyl phosphonate residue took place simultaneously. In addition, we confirmed that the chiral integrity of the leucine residue was preserved throughout these transformations. [ABSTRACT FROM AUTHOR]

The reaction of N -unprotected methylesters of phenylglycine derivatives ( 1a–1f ) with electron-rich internal alkynes ( 2a–2e ), catalyzed by [Ru(cymene)Cl 2 ] 2 (10%), gives the corresponding 3,4-disubstituted isoquinoline-1-carboxylates 3 through C H/N H oxidative coupling. The C H bond activation step is assisted by carboxylates, and N-fluoro-2,4,6-trimethylpyridinium triflate works as the terminal oxidant. The process shows a remarkable tolerance to the presence of diverse electron-releasing and electron-attracting functional groups at the phenyl ring of the amino acid. In addition, the reaction of phenylglycine derivatives ( 1a–1f ) with methyl acrylate ( 4a ) catalyzed by [Ru(cymene)Cl 2 ] 2 (10%) under the same experimental conditions, gives the corresponding 3, N -disubstituted isoindoline-1-carboxylates 5 through C H/N H coupling. Isoindolines 5 are obtained as a mixture of diastereoisomers, with moderate to high values of diastereomeric excess (up to 80%). [ABSTRACT FROM AUTHOR]

An overview of synthetic methods developed to build [ c]-fused bicyclic proline analogues is presented. The focus is on the preparation of azabicycles that bear a carbocyclic ring fused to the [ c] face of the pyrrolidine unit. Attention is paid both to procedures that afford the desired compounds in racemic form and to asymmetric strategies. Procedures are organized according to the size of the carbocycle that is fused to the pyrrolidine moiety. Strategies able to provide multigram quantities of enantiopure compounds that have application in the synthesis of marketed drugs are highlighted. [ABSTRACT FROM AUTHOR]

We report here the first practical and efficient synthesis of the diethyl 1,2,3,4-tetrahydro-β-carboline-3-phosphonates 3 and 4 as well as diethyl 9 H-β-carboline-3-phosphonates 5 and 6. The target compounds were prepared in good yields by application of the Pictet-Spengler reaction of easily obtainable phosphotryptophan diethyl ester 7. The procedure is based on simple preparation of racemic 7 followed by a Pictet-Spengler reaction with several aldehydes and subsequent oxidation chemistry. [ABSTRACT FROM AUTHOR]

A straightforward chemo-enzymaticsynthesis of new polyhydroxylatedbenzopyrrolizidines and cyclohexapyrrolizidinesis developed. The two-step strategy consists of l-fuculose-1-phosphatealdolase variant F131A-catalyzed aldol addition of dihydroxyacetonephosphate to rac-N-benzyloxycarbonylindoline-2-carbaldehydeas well as (2S*,3aS*,7aS*)- and (2S*,3aR*,7aR*)-N-benzyloxycarbonyloctahydroindole-2-carbaldehydesand a subsequent one-step catalytic deprotection–reductiveamination. [ABSTRACT FROM AUTHOR]

Abstract: The orthopalladation of methyl arylglycinate derivatives has been studied. The reaction proceeds efficiently for different electron-withdrawing and electron-releasing substituents at the aryl ring. The carbonylation of the orthopalladated complexes affords, in a single step, substituted (1H)-isoindolin-1-one-3-carboxylates. These compounds constitute valuable synthetic intermediates and can be transformed diastereoselectively into octahydroisoindole-1-carboxylic acid derivatives, an important scaffold in the synthesis of many biologically active compounds. [Copyright &y& Elsevier]

Abstract: High yielding and remarkably selective alkylations of a suitably protected derivative of (2S,3aS,7aS)-octahydroindole-2-carboxylic acid are described. The fused bicyclic structure of this proline analogue greatly influences the stereochemical outcome of direct alkylation reactions taking place at the α-carbon and provides access to α-substituted analogues with retention of the configuration. The overall procedure allows the preparation of enantiopure α-substituted derivatives of this Oic isomer, suitably protected for their incorporation into peptides, in a straightforward manner. [Copyright &y& Elsevier]

Abstract: A high yielding and remarkably stereoselective α-methylation reaction of the (2S,3aS,7aS)-stereoisomer of octahydroindole-2-carboxylic acid, (S,S,S)-Oic, suitably protected is described. The severe steric hindrance imposed by the fused cyclohexane ring, which prevents the application of Seebach’s self-reproduction of chirality methodology, accounts for the formation of (S,S,S)-(αMe)Oic with high selectivity and retention of configuration. [Copyright &y& Elsevier]

Abstract: An improved strategy for the effective synthesis of enantiomerically pure (2R,3aS,7aS)-octahydroindole-2-carboxylic acid (Oic), based on the formation of a trichloromethyloxazolidinone derivative, has been developed. Additionally, the completely diastereoselective α-alkylation of such oxazolidinone provides a very convenient and concise route to enantiopure α-tetrasubstituted derivatives of this Oic stereoisomer. [Copyright &y& Elsevier]

Abstract: The preparation of the proline analogue (2S,3aS,7aS)-octahydroindole-2-carboxylic acid (Oic) and its enantiomer, (2R,3aR,7aR)-Oic, is described. A racemic precursor has been synthesized in good yield and subjected to HPLC resolution on a chiral column. The high efficiency of both the synthetic and chromatographic procedures has allowed the isolation of multigram quantities of each amino acid in enantiomerically pure form and suitably protected for use in peptide synthesis. [Copyright &y& Elsevier]

Abstract: Nor-tropane related bicyclic (6+5) iminocyclitols with an ether bridge and different substituents (hydroxymethyl, aminomethyl, and aminoethyl) on C-1 are prepared starting from a β-d-psicofuranosyl cyanide. The method involves an internal nucleophilic attack of a stabilized amide ion on a 5-mesyloxy derivative. The intermediate N-acetyl O-protected iminocyclitols present atropoisomerism due to restricted rotation of the N–CO amido bond. Conformational aspects of the prepared compounds are discussed. [Copyright &y& Elsevier]

Abstract: Pyranoid and furanoid spiro-N-mesyl azetidines, a new type of water-soluble spiro-C-nucleoside, have been prepared from easily available sugar spiroacetals (or glycosyl cyanides). The synthetic pathway involves opening of the acetalic ring with trimethylsilylcyanide, reduction, formation of an N,O-dimesylate, cyclization with sodium hydride in anhydrous DMF, and O-deprotection. [Copyright &y& Elsevier]

The reaction of glycohexapyranosyl enamines, having 2- and 3-hydroxyl groups in a cis-relationship with 2,2-dimethoxypropane, induces ring contraction of the sugar ring with formation of 2,3-O-isopropylidene furanoid glycosylenamines. 5-O-Mesylation of these compounds, followed by formation of anhydroazasugars and nucleophilic ring opening, with thiols, produces alkyl and aryl thiofuranosides of 5-aminosugars [Copyright &y& Elsevier]

Bicyclic azasugar thioglycosides, a new type of azasugar and alkaloid derivative, are stereoselectively prepared from easily available glycosylenamines (d-gluco and l-rhamno configurations), via 1,4-anhydroazasugar derivatives. Polyhydroxylated pyrrolidines (nonreducing pyrrolidine azasugars) are also prepared by reduction with sodium cyanoborohydride of the same 1,4-anhydroazasugars. The stereochemical assignments of the new stereogenic centres are based on NMR experiments, including a study of the interproton distances from quantitative treatment of NOE data and molecular modeling. [Copyright &y& Elsevier]

Bicyclic (2-oxapyrrolizidines) and monocyclic (piperidine) azasugar ethyl thioglycosides, a new type of azasugar derivative, are stereoselectively prepared from suitable glycosylenamines, through anhydroazasugar derivatives. [Copyright &y& Elsevier]

Two new strategies for the efficient synthesis of racemic 1,2,3,4-tetrahydroisoquinoline-3-phosphonic acid (TicP) (±)-2 have been developed. The first strategy involves the electron-transfer reduction of the easily obtained α,β-dehydro phosphonophenylalanine followed by a Pictet–Spengler cyclization. The second strategy involves a radical decarboxylation–phosphorylation reaction on 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic). In both strategies, the highly electrophilic N-acyliminium ion is formed as a key intermediate, and the target compound is obtained in good yield using mild reaction conditions and readily available starting materials, complementing existing methodologies and contributing to the easy accessibility of (±)-2 for further research. [ABSTRACT FROM AUTHOR]

The Diels‐Alder reaction of 1‐aminovinylphosphonate esters has been studied for the first time as a suitable procedure leading to quaternary carbocyclic α‐aminophosphonates. The reaction is influenced by steric effects at the phosphonate functionality (bulky groups hinder the reaction) and electronic effects at the amino group (electron‐withdrawing substituents increase the reaction rate). The exo/endo ratio is constant, and no influence of the solvent is observed. The experimental results have been rationalized by DFT methods. 1‐Aminovinylphosphonate esters have been studied as Diels‐Alder reaction substrates for the first time. The influence on the course of the reaction of substituents and protecting groups on the phosphonate and amine functions has been considered and rationalized by DFT methods. [ABSTRACT FROM AUTHOR]

A diagram is presented which explains the synthesis of 3-phosphorylated ß-carboline derivatives through Pictet-Spengler reaction.

Review: [procedures that afford the desired compounds in racemic form and asymmetric strategies; 92 refs. [ABSTRACT FROM AUTHOR]

The article highlights the chemical equations involved in the synthesis of conformationally constrained iminocyclitols.

Review: 192 refs. [ABSTRACT FROM AUTHOR]

A simple dynamic kinetic resolution of dimethyl (1,3-dihydro-2 H -isoindol-1-yl)phosphonate has been developed by means of a lipase-catalyzed alkoxycarbonylation reaction. The influence of reaction parameters such as solvent, type and amount of alkoxycarbonylating agent, source and loading of enzyme, substrate concentration, temperature, and reaction time has been studied. The best results were found in the biocatalyzed reaction using Candida antarctica lipase type A and allyl 3-methoxyphenyl carbonate in toluene at 30 °C, yielding the ( R )-allyl carbamate in 58% isolated yield and 96% enantiomeric excess. Remarkably, this procedure does not require external auxiliaries for the racemization of the slow-reacting aminophosphonate enantiomer and occurs under mild reaction conditions. [ABSTRACT FROM AUTHOR]

α-Amino-C-phosphinic acids and derivatives are an important group of compounds of synthetic and medicinal interest and particular attention has been dedicated to their stereoselective synthesis in recent years. Among these, phosphinic pseudopeptides have acquired pharmacological importance in influencing physiologic and pathologic processes, primarily acting as inhibitors for proteolytic enzymes where molecular stereochemistry has proven to be critical. This review summarizes the latest developments in the asymmetric synthesis of acyclic and phosphacyclic α-amino-C-phosphinic acids and derivatives, following in the first case an order according to the strategy used, whereas for cyclic compounds the nitrogen embedding in the heterocyclic core is considered. In addition selected examples of pharmacological implications of title compounds are also disclosed. [ABSTRACT FROM AUTHOR]

We report here a practical and efficient synthesis of diethyl 1,2,3,4-tetrahydroisoquinoline-3-phosphonate derivatives. The target compounds were prepared in good yield using a Pictet-Spengler reaction involving α-amino phosphonates that were easily obtained. We have paid special attention to the synthesis of (R)- and (S)-1,2,3,4-tetrahydroisoquinoline-3-phos- phonic acid (TicP) 2a, a conformationally constrained analogue of phosphophenylalanine PheP. The procedure is based on the preparation of racemic phosphophenylalanine (PheP) diethyl ester followed by chiral chromatographic separation and subsequent Pictet-Spengler chemistry. [ABSTRACT FROM AUTHOR]

We report here a practical and efficient synthesis of diethyl 1,2,3,4-tetrahydroisoquinoline-3-phosphonate derivatives. The target compounds were prepared in good yield using a Pictet-Spengler reaction involving α-amino phosphonates that were easily obtained. We have paid special attention to the synthesis of ( R)- and ( S)-1,2,3,4-tetrahydroisoquinoline-3-phosphonic acid (TicP) 2a, a conformationally constrained analogue of phosphophenylalanine PheP. The procedure is based on the preparation of racemic phosphophenylalanine (PheP) diethyl ester followed by chiral chromatographic separation and subsequent Pictet-Spengler chemistry. [ABSTRACT FROM AUTHOR]

The preparation of enantiomerically pure pyrrolidine-2-phosphonic acid (phosphoproline, Pro P ) has been addressed through the synthesis of suitable racemates and subsequent resolution by independent enzyme-catalyzed and chiral HPLC methods. First, racemic phosphoproline derivatives bearing the necessary protecting groups have been synthesized in excellent global yields starting from inexpensive materials. Preparative HPLC resolution of the N -Cbz-protected aminophosphonate on a cellulose-based column allowed the isolation of enantiomerically pure enantiomers on a gram scale. Enzyme-catalyzed alkoxycarbonylation of the aminophosphonate was studied using different lipases, solvents, and carbonates. Candida antarctica lipase type A (CAL-A) provided the highest enantioselectivity when combined with benzyl 3-methoxyphenyl carbonate. [ABSTRACT FROM AUTHOR]

The proof-of-concept for the modular synthesis of new functional soft gel materials based on amide–triazole isosteric replacement has been demonstrated. A coassembly approach of isosteric amino acid-based hydrogelators was fruitfully applied for fine-tuning the release of entrapped drugs. [ABSTRACT FROM AUTHOR]

The orthopalladation, through CH bond activation, of a large number of amino esters and amino phosphonates derived from phenylglycine, and having different substituents at the aryl ring and the C-α atom, as well as on the N-amine atom, has been studied. The experimental observations indicated an improvement in the yields of the orthopalladated compounds when the N-amine and/or the C-α atom are substituted, when compared with the unsubstituted methyl phenylglycinate derivatives. In contrast, substitutions at the aryl ring do not promote significant changes in the orthometalation results. Furthermore, the use of hydrochloride salts of the amino esters has also been shown to have a remarkably favorable effect on the process. All these observations have been fully quantified at different temperatures and pressures by a detailed kinetic study in solution in different solvents and in the presence and absence of added Brønsted acids and chloride anions. The data collected indicate relevant changes in the process depending on these conditions, as expected from the general background known for cyclopalladation reactions. An electronic mechanism of the orthopalladation has been proposed based on DFT calculations at the B3LYP level, and a very good agreement between the trends kinetically measured and the theoretically calculated activation barriers has been obtained. The reactivity of the new orthopalladated amino phosphonate derivatives has been tested and it was found that their halogenation, alkoxylation and carbonylation resulted in formation of the corresponding functionalized ortho-haloaminophosphonates, ortho-alkoxyaminophosphonates and oxoisoindolinylphosphonates. [ABSTRACT FROM AUTHOR]

We present here the results obtained in our study on organocatalytic enantioselective Michael addition reaction of acetone to different nitroolefines using (2R,3aS,7aS)-octahydroindole-2-carboxylic acid [(R,S,S)-Oic] as a new and suitable catalyst for this process. Computational calculations support the results obtained with (R,S,S)-Oic versus its diastereomeric form (S,S,S)-Oic. The final products are obtained in good yields and moderate enantioselectivities (up to 58% ee). [ABSTRACT FROM AUTHOR]

We present here the results obtained in our study on organocatalytic enantioselective Michael addition reaction of acetone to different nitroolefines using (2R,3aS,7aS)-octahydroindole-2-carboxylic acid [(R,S,S)-Oic] as a new and suitable catalyst for this process. Computational calculations support the results obtained with (R,S,S)-Oic versus its diastereomeric form (S,S,S)-Oic. The final products are obtained in good yields and moderate enantioselectivities (up to 58% ee). [ABSTRACT FROM AUTHOR]

An abstract of the paper "First Synthesis of (R)- and (S)-1,2,3,4-Tetrahydroisoquinoline-3-phosphonic Acid (TicP) Using a Pictet-Spengler Reaction" is presented.

The organocatalytic activities of highly substituted proline esters obtained through asymmetric [3+2] cycloadditions of azomethine ylides derived from glycine iminoesters have been analyzed by 19F NMR and through kinetic isotope effects. Kinetic rate constants have been determined for unnatural proline esters incorporating different substituents. It has been found that exo- L and endo- L unnatural proline methyl esters yield opposite enantiomers in aldol reactions between cyclic ketones and aromatic aldehydes. The combined results reported in this study show subtle and remote effects that determine the organocatalytic behavior of these synthetic but readily available amino acid derivatives. These data can be used as design criteria for the development of new pyrrolidine-based organocatalysts. [ABSTRACT FROM AUTHOR]

Asymmetric syntheses of isoindoline carbamates have been successfully achieved through enzyme-mediated dynamic kinetic resolution processes and without requirement of metal or acid–base catalyst for the substrate racemization. Optically active carbamates were obtained in good yields and an excellent degree of stereoselectivity when Pseudomonas cepacialipase (PSL) was used as biocatalyst, with diallyl or dibenzyl carbonates being both adequate reagents in alkoxycarbonylation reactions. [ABSTRACT FROM AUTHOR]

Abstract: A series of α-amino acid derivatives containing the 2,3-dihydroindole or octahydroindole core have been chemoenzymatically synthesized in good overall yields and high enantiomeric purity under mild reaction conditions using lipases for the introduction of chirality. Candida antarctica lipase type A has shown excellent activity and high enantiodiscrimination ability toward the two cyclic amino esters used as substrates. The selectivity of the process proved to be greatly dependent on the alkoxycarbonylating agent. Thus, the enzymatic kinetic resolution of methyl indoline-2-carboxylate has been successfully achieved using 3-methoxyphenyl allyl carbonate, whereas (2R,3aR,7aR)-benzyl octahydroindole-2-carboxylate required the less reactive diallyl carbonate. [Copyright &y& Elsevier]

A new stereocontrolled and high yielding synthesis of biologically active polyhydroxyperhydroazepines is reported starting from easily available glycosylenamines (D-gluco, D-manno, and D-galacto configurations), which are transformed into 1,6-azaanhydropyranose derivatives. O- and N-Deprotection of the latter, followed by reduction with sodium cyanoborohydride, gives the target chiral iminocyclitols. The method is based on the capacity of the dialkoxycarbonylvinyl group to stabilize an amide ion, and the only limitation is the necessity for the starting glycosylenamine to have β-D-configuration. The inhibitory activity of several intermediate iminocyclitols and aldopyranosylenamines on different α- and β-glycosidases is also reported. [Copyright &y& Elsevier]

Review: [139 refs. [ABSTRACT FROM AUTHOR]