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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]

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]

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]

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]

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]

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]

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]

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]

Redox potentials for two stepwise anodic oxidations of a series of carbamates in methanolic solution have been calculated using ab initioand DFT quantum mechanical methods. Hartree–Fock method and Density Functional Theory at the B3LYP level, together with 6-31G(d), 6-31G(d,p) and 6-311++G(2df,2p) basis sets have been used for the calculation. The Polarizable Continuum Model (PCM) is used to describe the solute–solvent interactions of carbamates, and those of their radical-cations and cations. Linear relationships were observed between the theoretically predicted redox potential values and the corresponding anodic peak potentials obtained by cyclic voltammetry or the corresponding calculated energies of the Highest Occupied Molecular Orbital (HOMO) of these carbamates. [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]

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]