Enzo Santaniello

Lipase-catalyzed transesterification in organic solvents: Applications to the preparation of enantiomerically pure compounds

Abstract Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) can be used for the synthesis of esters by transesterification with activated and nonactivated acyl donors in organic solvents. The reaction is especially useful for the preparation of optically active compounds, which are formed by resolution or asymmetrization of racemic or prochiral suitable substrates. This review offers an overview of the state of the art through examples chosen from the most recent literature, focusing mainly on the preparation of enantiomerically pure products which can be formed by this enzymatic approach.

Polyetylene Glycols as host solvents: applications to organic synthesis☆

Abstract Polyethylene glycols (PEG) are fair solvents for inorganic salts and organic substrates; their use in some organic reactions is described.

Synthesis, physicochemical and spectroscopic characterization of copper(II)-polysaccharide pullulan complexes by UV–vis, ATR-FTIR, and EPR

Bioactive copper(II) complexes with polysaccharides, like pullulan and dextran, are important in both veterinary and human medicine for the treatment of hypochromic microcitary anemia and hypocupremia. In aqueous alkaline solutions, Cu(II) ion forms complexes with the exopolysaccharide pullulan and its reduced low-molecular derivative. The metal content and the solution composition depend on pH, temperature, and time of the reaction. The complexing process begins in a weak alkali solution (pH >7) and involves OH groups of pullulan monomer (glucopyranose) units. Complexes of Cu(II) ion with reduced low-molecular pullulan (RLMP, M(w) 6000 g mol(-1)) were synthesized in water solutions, at the boiling temperature and at different pH values ranging from 7.5 to 12. The Cu(II) complex formation with RLMP was analyzed by UV-vis spectrophotometry and other physicochemical methods. Spectroscopic characterizations (ATR-FTIR, FT-IRIS, and EPR) and spectra-structure correlation of Cu(II)-RLMP complexes were also carried out.

An efficient chemo-enzymatic approach to the enantioselective synthesis of 2-methyl-1,3-propamedical derivatives

Abstract Lipase-catalyzed transesterification of 2-methyl-1,3-propanediol 1 in chloroform affords enantiomerically pure (S)-(−)-acetate 2 , from which the (R)-(+)-silyl ethers 4a-b can be efficiently prepared (>98% ee). The (S)-TBDPS derivative 4b could be also efficiently and enantioselectively prepared by the same enzymatic procedure, starting from racemic 5b .

A total synthesis of mycophenolic acid, some analogues and some biogenetic intermediates

Abstract Mycophenolic acid (28) has been obtained by a convergent synthesis starting from methyl 6-bromo-4-methylhex-4-enoate (13) and 5,7-dihydroxy-4-methylphthalide (24). For the total synthesis of 5,7-dihydroxy-4-methylphthalide, 1-carbethoxy-2,3-dimethylcyclohexa-4,6-dione (14) was aromatized and transformed into 4,6-dimethoxy-2,3-dimethylbenzamide. The photolysis of the corresponding N-chloroamide and subsequent hydrolysis gave 5,7-dimethoxy-4-methylphthalide which was hydrolysed to 5,7-dihydroxy-4-methylphthalide (24). The bromoester (13) was obtained starting from geraniol. Condensation between 13 and 24 with silver oxide in dioxane afforded the methyl ester of nor-O-methyl mycophenolic acid. Selective methylation and hydrolysis furnished mycophenolic acid.

Apigenin 7-glucoside and its 2″- and 6″-acetates from ligulate flowers of Matricaria chamomilla

Abstract Dried ligulate flowers of Matricaria chamomilla contain 7–9% glucosides of apigenin and 0.3–0.5% free apigenin. Glucosides were identified as apigenin 7-glucoside and a 1:3 mixture of the 2″- and 6″-acetates, as determined by 13 C NMR analysis.

Enantioselective transesterification of 2-methyl-1,3-propanediol derivatives catalyzed by Pseudomonas fluorescens lipase in an organic solvent

Abstract The irreversible transesterification of racemic 2-methyl-1,3-propanediol derivatives, the monoethers, 3a , 3b , 5a , and the monobenzoate 5b , with vinyl acetate catalyzed by Pseudomonas fluorescens lipase in chloroform affords enantiomerically pure chiral synthons.

Evaluation of 3-hydroxy-3-methylglutaryl-CoA reductase activity by multiple-selected ion monitoring

Abstract A new method for the evaluation of 3-hydroxy-3-methylglutaryl-CoA reductase activity is described, based on the multiple-selected ion monitoring of the amount of mevalonate formed in incubations of 3-hydroxy-3-methylglutaryl-CoA with microsomal proteins. Analysis is carried out on crude extracts using deuterated mevalonic acid lactone as internal standard. The sensitivity of the technique allows the quantitative evaluation of mevalonate in microassays (100 μg microsomal protein) of the enzyme activity at the minimum value of the diurnal rhythm.

Focusing of pepsin in strongly acidic immunobilized pH gradients

A new acrylamido buffer has been synthesized, for use in isoelectric focusing in immobilized pH gradients. This compound (2-acrylamido glycolic acid) has a pK = 3.1 (at 25 degrees C, 20 mM concentration during titration) and is used, by titration with the pK 9.3 Immobiline, to produce a linear pH gradient in the pH 2.5-3.5 interval. Pepsin (from pig stomach) focused in this acidic pH gradient is resolved into four components, two major (with pI values 2.76 and 2.78) and two minor (having pI values 2.89 and 2.90). This is the first time that such strongly acidic proteins could be focused in an immobilized pH gradient. Even in conventional isoelectric focusing in amphoteric buffers it has been impossible to focus reproducibly very-low-pI macromolecules.

Bis-tetrabutylammonium Dichromate as a Neutral and Selective Oxidant of Hydroxy Compounds

Abstract The desire of mild reducing and oxidising reagents, which would be soluble in organic solvents, has led to the development of several tetraalkylammonium salts, such as borohydride2, cyanoborohydride3 and permanganate4.