Giuseppe Pedrocchi-Fantoni

Chemo-enzymatic alkylation of active methyleme compounds

Abstract Active methylene compounds undergo chemical condensation in water with aldehydes derived from yeast oxidation of the corresponding alcohols. Unsaturated compounds so obtained are then further reduced by yeast.

Crystallization and preliminary X-ray diffraction studies of phospholipase D from Streptomyces sp.

Crystals of purified phospholipase D (E.C. 3.1.4.4) from Streptomyces sp. strain PMF have been grown under two different crystallization conditions using vapour diffusion. Both conditions gave monoclinic crystals in space group P2(1). The unit-cell parameters were a = 57.28, b = 57.42, c = 68.70 A, beta = 93.17 degrees. The crystals diffract at 110 K to a resolution beyond 1.4 A using synchrotron radiation.

The substrate requirements of phospholipase D

The hydrolysis rates of different diphosphates, compared with the one observed with natural phosphatidylcholine, are used to identify the molecular basis for phospholipase D (PLD) catalysis. Experimental data strongly support the idea that PLD is a rather generic phosphodiesterase with very wide substrate specificity and a net preference for lipophilic substrates. The presence of choline in the polar head is not required for activity although it improves hydrolysis efficiency. Choline esters are found to be substrates for PLD hydrolysis, but only with long chain fatty acids.

On the mechanism of Baker's yeast mediated synthesis of (R) S-benzyl thioglycerate. Experiments in deuterated water

Abstract Experiments in ca. 90% deuterated water in which (R) S-benzyl thioglycerate (1) is obtained in the presence of benzyl mercaptan in bakers yeast fermenting on D-mannose, D-glucose and D-fructose, respectively, gave rise to trideuterated materials. The extent of labelling at various positions and the stereochemistry depends upon the carbohydrate used as precursor, as shown by 2H NMR studies onto the dioxolanes (12)-(14)

A biocatalytic resolution of chiral ketals, intermediates in the synthesis of azole drugs

Crude lipases are used for the resolution of racemic ketals advanced intermediates in the synthesis of cis-terconazole and cis-ketoconazole. Lipase from Aspergillus niger allows to obtain the (2R, 4R)-enantiomer of the imidazole-substituted ketal in good ee at low conversion. The addition of adsorbing resins improves the efficiency to interesting ee values for practical applications. The compound is transformed into (2R, 4S)-terconazole. The survived ester gives access to the other enantiomer.

Bis-phenacetyl and phenoxyacetyl groups as substrates for penG and penV amidases

o-, m-, p-Bis-phenylacetic and -bis-phenoxyacetic acid esters with solketal are prepared and submitted to enzymatic hydrolysis with penicillin V (PVA) and G (PGA) amidases. While the para-isomers are recovered unchanged, ortho- and meta-bis-esters are completely hydrolysed. PVA shows a reversed substrate specificity, hydrolysing phenylacetates faster than its natural substrate. The use of the bis-acids as alcohol-protecting groups is proposed.