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The synthesis of dehydrophos derivatives featuring modified peptide chains, characterized by the presence of substituents in the vinyl moiety, or possessing a phosphonic acid monoalkyl ester other than the monomethyl ester one, has been accomplished by a versatile procedure based on Horner-Wadsworth-Emmons olefination with suitable aldehydes and on the selective hydrolysis of the dialkyl phosphonate group. Such derivatives have been tested against a series of bacterial strains, using the naturally occurring peptide, dehydrophos, for comparison. Thus, the effects of the aforementioned structural variations on antimicrobial activity have been studied.

trans-Fused octahydroisoindole-1-carboxylic acids are bicyclic proline analogues of potential interest in the search for new drugs. Within this work, the trans-fused octahydroisoindole system has been constructed using methyl trans-2-(hydroxymethyl)cyclohexane-1-carboxylate as the key synthetic precursor, in turn readily prepared from inexpensive cis-cyclohexane-1,2-dicarboxylic anhydride. Both the (1S*,3aR*,7aR*)- and the (1R*,3aR*,7aR*)-octahydroisoindole-1-carboxylic acids were prepared through the Strecker reaction of methyl trans-2-formylcyclohexane-1-carboxylate as the key step. Finally, (1S*,3aR*,7aR*)-octahydroisoindole-1-carboxylic acid was obtained with good yields in a highly stereoselective manner using (3aR*,7aR*)-octahydroisoindole-1-one as a suitable scaffold.

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.

The reaction of N-unprotected methylesters of phenylglycine derivatives (1a–1f) with electron-rich internal alkynes (2a–2e), catalyzed by [Ru(cymene)Cl] (10%), gives the corresponding 3,4-disubstituted isoquinoline-1-carboxylates 3 through C[sbnd]H/N[sbnd]H oxidative coupling. The C[sbnd]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] (10%) under the same experimental conditions, gives the corresponding 3,N-disubstituted isoindoline-1-carboxylates 5 through C[sbnd]H/N[sbnd]H coupling. Isoindolines 5 are obtained as a mixture of diastereoisomers, with moderate to high values of diastereomeric excess (up to 80%).

A simple dynamic kinetic resolution of dimethyl (1,3-dihydro-2H-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.

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.

The preparation of enantiomerically pure pyrrolidine-2-phosphonic acid (phosphoproline, Pro) 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.

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.

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. Densely substituted enantiopure proline esters obtained through [3+2] cycloadditions catalyze aldol reactions. These synthetic organocatalysts produce different enantiomeric aldol adducts depending on the stereochemical dispositions of the substituents at distal positions with respect to the catalytic site. Design criteria are proposed for this kind of organocatalysts.

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 or-ganized 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.

A lo largo de esta tesis doctoral se han desarrollado diferentes estrategias sintéticas para la preparación de análogos de prolina que presentan un ciclo de seis miembros (benceno o ciclohexano) fusionado en las caras [c] o [d] del anillo de pirrolidina. Las estrategias empleadas se basan en reacciones estereoselectivas y procesos de resolución cromatografía o enzimatica. Mediante estos procedimientos, los aminoácidos objetivo han sido aislados con buen rendimiento global y, en algunos, en forma enantiopura. Los análogos de prolina obtenidos se basan en la estructura de indol e isoindol, y han sido utilizados para diferentes aplicaciones.

A straightforward chemo-enzymatic synthesis of new polyhydroxylated benzopyrrolizidines and cyclohexapyrrolizidines is developed. The two-step strategy consists of l-fuculose-1-phosphate aldolase variant F131A-catalyzed aldol addition of dihydroxyacetone phosphate to rac-N-benzyloxycarbonylindoline- 2-carbaldehyde as well as (2S*,3aS*,7aS*)- and (2S*,3aR*,7aR*)-N-benzyloxycarbonyloctahydroindole-2- carbaldehydes and a subsequent one-step catalytic deprotection-reductive amination. © 2014 American Chemical Society.