Regio- and Stereoselective Synthesis

An area where regio- and stereoselective synthesis with biocatalysts is particularly attractive because of highly specific reactions are carbohydrate synthesis and glycosylation of natural products [24, 25]. We have prepared a series of glycosyl 

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Regio- and stereoselective synthesis of y-alkylidenebutenolides and related compounds 97T6707. 

The developments highlighted in this chapter show that vinylepoxides are readily available starting materials. Several techniques for their regio- and stereoselective synthesis and derivatization exist, and it is consequently to be expected that the use of vinylepoxides as substrates in organic synthesis will increase. 

Similarly, cycloaddition of the cyclohexenone-like dienophile 40 with 2-tri-methylsilyloxy-1,3-butadiene (41) allowed [7] the regio- and stereoselective synthesis of tetracyclic compound 42, in high yield (Equation 5.5). 

In recent years, Hoppe s group has considerably extended the isomerization-addition methodology, especially for the highly regio- and stereoselective synthesis of 1,2-alkadienyl carbamates. It involves deprotonation of alkynyl carbamates, transme-talation into a titanium species and subsequent reaction with carbonyl compounds [26-30]. This group recently described the preparation of enantiomerically enriched 4-hydroxyallenyl carbamates 22 by sparteine-mediated lithiation of alkynyl carbamates 20 [29]. Impressive examples of these transformations are summarized in Scheme 8.8. 

DFT Based Analysis for The Regio- and Stereoselective Synthesis of Tetrasubstituted Isoxazolidines From Cinnamoyl Piperidine Derivatives... 

Borzilleri RM, Zheng X, Schmidt RJ, Johnson JA, Kim S-H, DiMarco JD, Fairchild CR, Gougoutas JZ, Lee FYF, Long BH, Vite GD. (2000) A novel application of a pd(0)-catalyzed nucleophilic substitution reaction to the regio- and stereoselective synthesis of lactam analogues of the epothilone natural products. J Am Chem Soc 122 8890-8897. 

A. Otaka, F. Katagiri, T. Kinoshita, Y. Odagaki, S. Oishi, H. Tamamura, N. Hamanaka, N. Fujii, Regio- and stereoselective synthesis of ( )-Alkene frans-Xaa-Pro dipeptide mimetics utilizing organocopper-mediated Anti-S M2 reactions, J. Org. Chem. 

T. Murase, H. Ishida, M. Kiso, and A. Hasegawa, A facile regio- and stereoselective synthesis of a-glycosides of W-acetylneuraminic acid, Carbohydr. Res. 184 Cl (1988). 

Moreover, using the same starting materials, they have reported the regio- and stereoselective synthesis of enantiopure or racemic benzofused tricyclic (3-lactams such as benzocarbapenems and benzocarbacephems (III and IV, Fig. 17) via intramolecular aryl radical cyclization [287]. 

A highly regio- and stereoselective synthesis of oxepine derivatives via cyclization of bromoallenes bound with hydroxy group by a four-carbon atom tether in the presence of a palladium(O) catalyst and alcohol is developed (Equation 16). In this reaction, the bromoallenes act as an allyl dication equivalent, and the intramolecular nucleophilic attack takes place exclusively at the central carbon atom of the allene moiety <2004JA8744>. 

A highly regio- and stereoselective synthesis of 3-arylidene-l,4-benzodioxepin-5-ones has been achieved with palladium-copper catalysis (Scheme 7) <2000J(P1)775>. 

Allylsilanes. A regio- and stereoselective synthesis of allylsilanes involves nickel-catalyzed coupling of enol phosphates with trimethylsilylmcthylmagnesium chloride... 

I - Alkyny lphenyl selenides. Benzeneselenenyl bromide and silver nitrite (1 equiv.) rcncl to form a reagent (presumably C6H5SeN02) that converts 1-alkynes into 1-nlkynyl phenyl selenides (equation I).1 The same reaction has been effected in generally lower yields with phenyl selenocyanate catalyzed by Cu(I).2 The products tire useful intermediates for regio- and stereoselective synthesis of vinyl selenides. 

Coupling the hydroboration with a subsequent oxidation of the new formed borane yields a //-Markovnikov alcohols. The hydroboration/oxidation sequence constitutes a powerful method for the regio- and stereoselective synthesis of alcohols. 

Benedetti, F. Berti, F. Norbedo, S. Ring-opening of epoxyalcohols by Et2AlCN. Regio- and stereoselective synthesis of l-cyano-2,3-diols. Tetrahedron Lett. 1999, 40,1041—1044. 

Bonafoux, D. Bordeau, M. Biran, C. Cazeau, P. Dunogues, J. Regio- and stereoselective synthesis of silyl enol ethers using a new base electrogenerated from HN(SiMe3)2. J. Org. Chem. 1996, 63, 5532-5536. 

Kumar RR, Perumal S, Senthilkumar P et al (2008) A highly atom economic, chemo-, regio-and stereoselective synthesis, and discovery of spiro-pyrido-pyrrolizines and pyrrolidines as antimycobacterial agents. Tetrahedron 64 2962-2971... 

Changing the transition-metal from palladium to rhodium (equation 62) makes possible, in addition to the straight-chain alkylation product (243), the regio- and stereoselective synthesis of amino acid derivatives with a terminal double bond (242), starting from optically active branched allylic substrates 241 (Table 21)" . Remarkably, the substitution products were obtained with high enantiomeric excesses, what might result from a slow isomerization of the intermediary formed allyl rhodium complexes ". 

TABLE 21. Regio- and stereoselective synthesis of amino adds by rhodium-catalyzed aUyUc alkylation (equation 62)... 

Negishi, E.-E Kotora, M. Regio- and Stereoselective Synthesis of y-Alkylidenebutenolides and Related Compounds, Tetrahedron 1997, 53, 6707-6738. 

Zhu, Y, Kong, F, Regio- and stereoselective synthesis of 1—>6 linked manno-, gluco-, and galactopyranose di-, tri-, and tetrasaccharides via orthoester intermediates, J. Carbohydr. Chem., 19, 837-848, 2000. 

Murata, M., Watanabe, S., Masuda, Y. Regio- and stereoselective synthesis of allylboranes via platinum(0)-catalyzed borylation of allyl halides with pinacolborane. Tetrahedron Lett. 2000, 41, 5877-5880. 

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