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An effective stereocontrolled synthesis of the HIV protease inhibitor Nelfinavir is reported. Two transformations were identified crucial for achieving success: the formation of a densely functionalized α-chloroketone via the homologation of a Weinreb amide with chloromethyllithium (LiCH2Cl), followed by its erythro selective reduction into the corresponding chiral chlorohydrin. A commercially available enzyme P2-C02 was particularly well suited for this purpose, affording the key alcohol (in an excellent 99% de), which was then smoothly converted into the active biologically active agent.

The first described acylation of a primary diol possessing a prochiral quaternary center catalyzed by lipase TL from Pseudomonas stutzeri is described. Optimized conditions were designed by testing different experimental conditions on model substrates (cyclopentylmethanol, cyclohexylmethanol, cyclopentane-1,1-diyldimethanol or cyclohexane-1,1-diyldimethanol) to find best organic solvent, optimal acyl donor and temperature, as well as the optimal substrates/enzyme ratio. Lipase TL resulted the best biocatalyst, while vinyl butyrate as acylating agent and a mixture of isooctane/THF 8/2, (v/v) resulted the best experimental conditions. Under these conditions, reaction were monitorized by chiral HPLC (diffraction index detector). The enantiomeric excess in the acylation of target substrate, (tetrahydro-2 H -pyran-2,2-diyl)dimethanol, was measured by derivatization of monoesters with Mosher's R -MTPA-Cl, which also was useful to determine the S absolute configuration of the major reaction product of the lipase-catalyzed monoacylation.

Water/organic solvent two-liquid-phase systems have been successfully applied in the synthesis of enantiomerically pure ( S )-benzoin through two different methodologies catalysed by whole cells from the non-conventional yeast Pichia glucozyma : the stereoselective monoreduction of benzil and the deracemisation of benzoin. The presence of the organic solvent influences the redox systems implied in the reactions, avoiding the formation of the corresponding diols, increasing the enantioselectivity and allowing the easy isolation of the products in high yields and excellent enantiomeric excesses. The use of both strategies has been extended to the preparation of different chiral benzoin derivatives.

A chemoenzymatic Dynamic Kinetic Resolution (DKR) of unsymmetrical benzoins (Ar1≠Ar2) has been carried out, by using Pseudomonas stutzeri lipase stereorecognition pattern. After studying this lipase behaviour, a high preference towards acylation of those benzoins containing substituents in the phenyl ring rather than in the benzoyl moiety was observed. This fact allowed the development of the DKR process of this kind of substrates, avoiding the accumulation of secondary products derived from the in situ racemization mediated by Shvo’s catalyst action, and allowing the synthesis of enantiopure unsymmetrical benzoins acetates (not previously described) in very good yields (60–95%) and excellent enantiomeric excess values (always >99%).

In this work we have studied the monoreduction of different 1,2-diaryl-ethanediones (benzils, 1) with lyophilised whole cells from Pichia glucozyma CBS 5766, using the diphenyl compound (benzil, 1a) as model substrate, and extended the enantioselective reduction to structurally different symmetric benzils for producing enantiomerically pure or enriched benzoins (α-hydroxyketones 2) in high yields and very short reaction times. In order to study the regio- and stereoselectivity of this biocatalyst, we examined the reduction of diaryldiketones formed from different aryl moieties, to obtain symmetric and asymmetric crossed-benzoins. This methodology is conducted under very mild reaction conditions (aqueous media with small amounts of DMSO for solubilising the substrates, T=28 °C), therefore constituting a green alternative compared to other reported procedures for obtaining homochiral benzoins.

Asymmetric benzoin condensation was performed using recombinant benzaldehyde lyase (BAL) from Pseudomonas fluorescens Biovar I. To enable the conversion of hydrophobic substrates, the enzyme was entrapped in polyvinyl alcohol and suspended in hexane. Compared to the reported application of the biocatalyst in an aqueous phase containing 20% DMSO, the productivity of the resulting gel-stabilised two-phase system was 3-fold better. The entrapment process had an efficiency of >90%, no enzyme or cofactor was lost during reaction or storage. The entrapped enzyme was stable in hexane for 1 week at 4 °C and more than 1 month at −20 °C. Without preceding optimisation the novel benzoins (R)-1,2-di(3-furanyl)-2-hydroxyethanone, (R)-2-hydroxy-1,2-di(3-thienyl) ethanone, (R)-1,2-di(4-ethoxyphenyl)-2-hydroxyethanone, (R)-1,2-di(3-ethoxyphenyl)-2-hydroxyethanone, (R)-2-hydroxy-1,2-di(3-tolyl)ethanone, and (R)-1,2-di(benzofuran-2-yl)-2-hydroxyethanone were prepared with yields up to 31.8% and enantiomeric excess >99%.

The regioselective acylation of phenylalkanediols catalysed by porcine pancreatic lipase (PPL) was the reaction used for modelling different areas in the active site of the enzyme. With this aim, different racemic or prochiral (1,n)-diols, with n ranging from 2 to 6 were resolved via transesterification with vinyl acetate, and the results were explained according to microcrystalline enzyme structure. Thus, we describe a logical model for explaining the enzyme regio and stereoselectivity, based on three residues of the active site (Ser153, Phe216 and His264) which turned out to be crucial for the substrate binding and transformation.

Different racemic or prochiral phenyl alkane (l,n)-diols were synthesized, and their resolution was carried out by two different strategies: enzymatic transesterification with vinyl acetate, or enzymatic hydrolysis of their corresponding diacetates, in both cases catalysed by porcine pancreatic lipase (PPL). The absolute configuration of the optically enriched reaction products was determined by formation of Mosher's esters or by the use of the Benzene Sector and Benzene Chirality Rules as obtained from the Circular Dichroism spectra.