Mycoparasitic Trichoderma strains secrete a complex set of hydrolytic enzymes under conditions related to antagonism. Several proteins with proteolytic activity were detected in culture filtrates from T. harzianum CECT 2413 grown in fungal cell walls or chitin and the protein responsible for the main activity (PRA1) was purified to homogeneity. The enzyme was monomeric, its estimated molecular mass was 28 kDa (SDS-PAGE), and its isoelectric point 4.7-4.9. The substrate specificity and inhibition profile of the enzyme correspond to a serine-protease with trypsin activity. Synthetic oligonucleotide primers based on N-terminal and internal sequences of the protein were designed to clone a full cDNA corresponding to PRA1. The protein sequence showed <43% identity to mammal trypsins and 47-57% to other fungal trypsin-like proteins described thus far. Northern analysis indicated that PRA1 is induced by conditions simulating antagonism, is subject to nitrogen and carbon derepression, and is affected by pH in the culture media. The number of hatched eggs of the root-knot nematode Meloidogyne incognita was significantly reduced after incubation with pure PRA1 preparations. This nematicidal effect was improved using fungal culture filtrates, suggesting that PRA1 has additive or synergistic effects with other proteins produced during the antagonistic activity of T. harzianum CECT 2413. A role for PRA1 in the protection of plants against pests and pathogens provided by T. harzianum CECT 2413 is proposed.

A synthetic route to imino thioglycosides and to imino sulfinylglycosides has been developed. A detailed study on the diastereoselective oxidation of 2-amino-2-deoxy-1-thio-beta-D-glucopyranosides is reported. It has been shown that the stereochemical outcome of the oxidation is highly dependent on the protective group of the amine function. While the oxidation of iminothioglycosides is slightly diastereoselective (up to 30% de in favor of the R(S) sulfoxide), a single isomer is obtained in the case of tetrachlorophthalimido derivatives. The absolute configuration of the sulfinyl glycoside was ascertained by NMR analysis using our recent model on the basis of the exo-anomeric effect corroborated by X-ray crystallography.

Phosphinite thioglycosides I for which a modular synthetic approach is reported, were found highly efficient catalyst precursors for palladium(0)-catalyzed asymmetric substitution. Both enantiomers of the allylated products have been obtained with high ee (up to 96%) using natural sugars as catalyst precursors.Key words: P/S ligands, carbohydrates, both enantiomers, allylic substitutionThe difficulty to predict the structural requirements of a ligand for acting as a successful catalyst explains the enduring need to develop new ligands which combine efficiency, wide scope and easy synthesis.1 Therefore, modular synthetic designs allowing a rapid optimization of the ligand structure for a high activity and/or selectivity in a precise chemical transformation are greatly desirable. Carbohydrates, which are amongst the cheapest and most abundant chiral starting materials, hold a range of structural characteristics that make them very appealing for such venture.2 Notably, carbohydrates possess various hydroxyl groups in different orientations, allowing easy tuning of steric, electronic and three-dimensional structure of carbohydrate based ligands.3 Conceptually, the utilization of carbohydrates in asymmetric synthesis is severely limited when both enantiomers are needed, as Lsugars are exceedingly expensive. While this problem has been elegantly solved by RajanBabu 4 in the case of homodonor P/P ligands, up to now there is no solution in the case of mixed ligands with two different heteroatoms.Following the seminal work of Evans, 5 in this communication we report the first synthesis of mixed P/S ligands I derived from carbohydrates (Scheme 1), and their preliminary applications in a highly enantioselective palladium(0)-catalyzed allylic substitution. In our approximation both enantiomers of the allylated products have been obtained using pseudo-enantiomeric natural sugars as catalyst precursors. 6A fundamental characteristic of the phosphinite thioglycoside I is that upon coordination to the metal the anomeric sulfur atom becomes stereogenic. The close proximity of the chiral sulfur atom to the coordination sphere of the transition metal anticipates a good enantioselective discrimination in the catalytic process, provided that the low inversion barrier of the sulfur metal bond can be surmounted. 5,7 We have recently reported the preparation of C 2 -symmetric bis-thioglycosides as new homodonor S/S ligands in Pd(0)-catalyzed allylic alkylation of 1,3-diphenylpropenylacetate with dimethyl malonate.8 A subsequent study of the corresponding Pd(II) complexes has indicated that the good enantioselectivity achieved was a consequence of an efficient stereocontrol of the sulfur atom exerted by the exo-anomeric effect. 9 In the case of phosphinite thioglycosides I metal complexes, where the exo-anomeric effect is not operative, good stereocontrol of the sulfur atom is also predicted taking into account the strong steric and stereoelectronic interactions of the substituent at sulfur and the endocyclic oxygen of the py...

Treatment of several C(2) symmetric bis-thioglycosides with Pd(CH(3)CN)(2)Cl(2) always leads to a single diastereomeric Pd(II) complex as a consequence of the exo-anomeric effect.