Stereoselective synthesis, also

Stereoselective Strecker reactions with galactosylamine 1 can also be achieved with sodium cyanide and acetic acid in 2-propanol. The reactions, however, proceed slowly and with a lower stereoselectivity, giving diastereomeric ratios of the products between 3 1 and 7 1. The scope of the method can be extended to other glycosylamines, e.g., 2,3,4-tri-O-pivaloyl-a-D-arabinosyl-amine which allows the stereoselective synthesis of (A )-amino nitriles61,62. 

A low stereoselection is also reported for an Ugi reaction which is the central step in the total synthesis of the antibiotic ( + )-furanomycin80. The carbohydrate-derived intermediate, formed from the following acetal and (+ )-a-methyIbenzylamine, reacts with benzoic acid and tert-butyl isocyanide to deliver the precursor 2 of the antibiotic and its diastcreomer 3 in equal amounts80. 

Consecutive Michael additions and alkylations can also be used for the diastereoselective synthesis of 5- and 6-membered ring systems. For instance when 6-iodo-2-hexenoates or 7-iodo-2-heptenoates are employed the enolate of the Michael adduct is stereoselectively quenched in situ to provide the cyclic compound with trans stereochemistry (>94 6 diastereomeric ratio). As the enolate geometry of the Michael donor can be controlled, high stereoselectivity can also be reached towards either the syn or anti configuration at the exocyclic... 

The stereoselective synthesis of hexacoordinated phosphate anions was also reported by the same group. A general one-pot process was developed for the preparation of C2-symmetric anions 15,16 and 17 containing enantiopure BINOL, hydrobenzoin, and tartrate-derived ligands respectively [38-40] Cpsymmetric anion 18 being prepared similarly in two steps from methyl-a-... 

An in depth account of intramolecular 1,3-dipoIar cycloadditions involving dipoles such as nitrUe oxides, sUyl nitronates, H-nitrones, azides, and nitrUimines is presented with particular emphasis on the stereochemistry during the cycloaddition. Various methods employed for the generation of the dipoles and their applications to stereoselective synthesis are also discussed. 

Other chiral ligands such as BINAP (where BINAP is bis(diarylphosphino)-1,1 binaphthyl) or aminophosphines are also efficient for stereoselective synthesis of chiral-at-metal Ru complexes [39-41]. 

Stereoselective synthesis can also be carried out in the case of tetrahedral complexes. An interesting example was described in 2001 (Fig. 8) [42]. 

Methyl diazoacetate is also decomposed on Raney nickel to give quantitatively a mixture of dimethyl fumarate and maleate 369) N2 evolution is observed even at room temperature. Most remarkably, dimethyl maleate is formed with high stereoselectivity (at 70 °C 92% of dimethyl maleate, 7% of dimethyl fumarate 370)). This represents one of the few cases of stereoselective synthesis on metal surfaces which have been found so far. 

The resulting derivatives (269) can be considered as strategically important intermediates in the synthesis of glycosidase inhibitors and carbocyclic nucleosides (150). A new approach to the stereoselective synthesis of the piperidine ring with the use of [4+ 2] [3+ 2]-cycloaddition from specially prepared substrates is also very interesting (431)b, c. In the context of this problem, the conditions for the formation of systems containing quaternary vicinal stereocenters were found. 

Jean Rodriguez was born in Gieza, Spain, on 25 June 1958, and in 1959 his family emigrated to France. After studying chemistry at the University Paul Cezanne in Marseille, France, he completed his PhD as a CNRS student with Prof. B. Waegell and Prof. P. Brun in 1987. He completed his Habilitation in 1992, also at Marseille, where he is currently Professor and Director of the UMR-CNRS-6178-SYMBIO. His research interests include the development of domino and multicomponent reactions, and their applications in stereoselective synthesis. In 1998, he was awarded the Acros prize in Organic Chemistry from the French Chemical Society. 

Chirality element enumeration is essential for the classification of stereoselective reactions 27>. For instance, in order to distinguish an asymmetrically induced synthesis from other reactions whose stereoselectivity is also due to a chiral reference system, one must compare the number of chirality elements in the starting materials and the products. 

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