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The totally diastereoselective synthesis of new P-stereogenic (o-hydroxyaryl)diazaphospholidines, in the form of their borane complexes 4a–4h, is described. The efficiency of this procedure is based both, on a one-pot and totally diastereoselective synthesis of the precursors (ortho-bromoaryloxy)diazaphosphospholidine–borane complexes 3a–3h, and on a stereoselective P–O to P–C migration rearrangement. A X-ray diffraction study of the structures of the product 4f and his precursor 3f shows unambiguously the totally stereoselectivity of the P–O to P–C rearrangement with clean retention of the phosphorus configuration.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The synthesis of a new class of bifunctional organophosphorus catalysts for the asymmetric borane reduction of prochiral ketones has been investigated. Keys to the architecture of effective catalysts are an oxazaphospholidine structural unit and a hydroxyaryl moiety. These (o-hydroxyaryl)oxazaphospholidine oxides have been successfully applied to the catalytic (2 mol-%) asymmetric borane reduction of numerous prochiral ketones with enantiomeric excesses up to 84% ee.

The use of a new chiral copper catalyst involving QUIPHOS as ligand in the 1,4-addition of Et2Zn to enones is reported. The dramatic beneficial effect of addition of water or Zn(OH)2 to this system has been investigated, and led to an improvement of the enantiomeric excess from 7 to 61% ee.

The palladium(0)-catalyzed alkylation of 2,3-bis(acetoxymethyl)bicyclo[2.2.1]hepta-2,5-diene 1 with malonate-type enolates as nucleophiles is investigated. A monoalkylated product is formed first, and undergoes (depending on the nucleophile used) a second intramolecular reaction leading to spirocyclopropane-annulated bicyclo[2.2.1]heptene derivatives 5. The formation of endo spirobicyclic cyclopropanes adducts as major isomer is rationalized by assuming formation of an intermediate exo-(π-allyl)palladium complex.

Phosphonate compounds mimic the first transition state occurring during enzymatic carboxyester hydrolysis of natural substrates by forming a covalent bond with the catalytic serine. However, until now the organophosphorus compounds used in the inhibition studies more or less resembled a natural triglyceride substrate. In order to elucidate the interfacial activation and the mechanism of action of lipases, specific inhibitors need to be prepared. To achieve this goal, enantiomerically pure sn-1,2- and sn-2,3-O-didecanoylglycerol compounds were prepared – starting from a C-4 chiral synthon, 3-buten-1,2-diol – and treated with n-pentylphosphonic dichloride and p-nitrophenol to afford the corresponding diastereomeric phosphonates, which were acylglycerol analogs. Subsequent separation of each of the phosphonate diastereomers A/B or ent-A/ent-B, performed by HPLC, led to four enantiopure stereoisomers that will be investigated as inhibitors of Human Pancreatic Lipase (HPL) and Human Gastric Lipase (HGL) using the monomolecular film technique.

The totally regio- and stereoselective P–O-to-P–C rearrangement in the synthesis of various chiral P-(o-hydroxyaryl)diazaphospholidine P-oxides has been investigated. This reaction proceeds with excellent yields ranging from 72 to 92%, total retention of configuration at the phosphorus atom, and complete regioselectivity. An exception was found with naphthyl derivatives, which gave mixtures of two regioisomers. In all cases, the products generated have been unambiguously characterized by 1H-, 13C-, and 31P-NMR spectroscopy as well as by X-ray-diffraction analysis.

The synthesis of a new class of chiral o-methoxydiazaphosphonamides (as Lewis bases) has been investigated, together with their use as catalysts in the asymmetric ring opening (ARO) of cyclooctene oxide with silicon tetrachloride. Enantiomeric excesses varying from 6 to 99% ee were observed, depending on the nature of the catalyst examined. On the basis of experimental considerations, a mechanistic rationale involving hexacoordinate silicon species has been proposed.