P stereoselective syntheses

Bernard A, Arosio D, Manzoni L, Micheli F, Pasqnarello A, Seneci P. Stereoselective synthesis of conformationally constrained cyclohexanediols a set of molecnlar scaffolds for the synthesis of glycomimetics. J. Org. Chem. 2001 66 6209-6216. Arosio D, Vrasidas I, Valentin P, Liskamp RM, Pieters RJ, Bemardi A. Synthesis and cholera toxin binding properties of mnltivalent GMl mimics. Org. Biomol. Chem. 2004 2 2113-2124. 

Cao, X.-P. Stereoselective synthesis of substituted all-trans 1,3,5,7-octatetraenes by a modified Ramberg-Backlund reaction. Tetrahedron 2002, 58, 1301-1307. 

McCarthy, J.R., Matthews, D.P, and Paolini, J.P, Stereoselective synthesis of 2,2-disubstituted 1-fluoroalkenes. ( )- [Fluoro(2-phenylcyclohexylidene)methyl]sulfonyl benzene and (Z)-[2-(fluoro-methylene)cyclohexyl]benzene, Org. Synth., 72, 216, 1993. 

Nicotra, F., Panza, L., Russo, G., Senaldi, A., Burlini, N., and Tortora, P., Stereoselective synthesis of the isosteric bisphosphono analogue of P-D-lfuctose-2,6-bisphosphate, J. Chem. Soc., Chem. Commun., 1396, 1990. 

Lavallee, J.-R, Spino. C.. Ruel. R.. Hogan. K.T., and Deslongchamps, P, Stereoselective synthesis of cw-decalins via Diels-Alder and double Michael addition of substituted Nazarov reagents. Can. J. Chem., 70, 1406. 1992. 

Bissel P, Nazih A, Sablong R, Lepoittevin J-P. Stereoselective synthesis of (R)- and (S)-4-methoxydalbergione via asymmetric catalytic hydrogenation. Org. Lett. 1999 1 1283-1285. 

Desroy N, Le Roux R, Phansavath P, Chiummiento L, Bonini C, Genet J-P. Stereoselective synthesis of C15-C24 and C25-C30 fragments of dolabeUdes. Tetrahedron Lett. 2003 44(9) 1763-1766. 

Total syntheses have been reported by E.J. Corey (1978B, 1979). We outline only the stereoselective synthesis of a protected fragment (A) which contains carbon atoms 1—9. This fragment was combined with fragment (B) by a Grignard reaction and cyclized by one of the methods typical for macrolide formation (see p. 146). 

A -0-2-Isocephem-4-carboxylic acid, 1-P-phenoxyacetamido-3-methyl-1 -oxo-synthesis, 1, 430 Isochroman, 1,3-diphenyl-synthesis, 3, 787, 788 Isochroman, 3,4-diphenyI-conformation, 3, 631 Isochroman, 2-methyl-synthesis, 3, 788 Isochroman, 3-phenyl-synthesis, 3, 788 Isochroman, (-)-)-(i )-3-phenyI-stereoselective synthesis, 3, 789 Isochroman-4-carboxylic acid, l-oxo-3-phenyl-synthesis, 3, 860 Isochroman-I,3-diones, 4-acyI-synthesis, 3, 831 Isochromanols dehydration, 3, 767 isochroman synthesis from, 3, 789 Isochroman-1-one, 3-aryl-synthesis, 3, 858, 860... 

Darzens reaction can be used to efficiently complete the stereoselective synthesis of a"-substituted epoxy ketones. As an example, Enders and Hett reported a technique for the asymmetric synthesis of a"-silylated a,P-epoxy ketones. Thus, optically active a -silyl a-bromoketone 38 was treated with LDA followed by the addition of benzaldehyde to give a"-silyl epoxyketone 40 in 66% yield with good... 

Solanesol and other prenyl alcohols are important as metabolites in mulberry and tobacco leaves and in the synthesis of isoprenoid quinones. Hence, Sato and collaborators107 have developed a stereoselective synthesis of all-trans-polyprenol alcohols up to C50. Construction of the requisite skeletons was accomplished by the alkylation of a p-toluenesulphonyl-stabilized carbanion, followed by reductive desulphonylation of the resulting allylic sulphonyl group. This was achieved most efficiently by the use of a large excess of lithium metal in ethylamine (equation (43)), although all reaction conditions led to mixtures. The minor product results from double bond rearrangement. 

This procedure illustrates a general method for the stereoselective synthesis of ( P)-disubstitnted alkenyl alcohols. The reductive elimination of cyclic /3-halo-ethers with metals was first introduced by Paul3 and one example, the conversion of tetrahydrofurfuryl chloride [2-(chloromethyl)tetrahydrofuran] to 4-penten-l-ol, is described in an earlier volume of this series.4 In 1947 Paul and Riobe5 prepared 4-nonen-l-ol by this method, and the general method has subsequently been applied to obtain alkenyl alcohols with other substitution patterns.2,6-8 (I )-4-Hexen-l-ol has been prepared by this method9 and in lower yield by an analogous reaction with 3-bromo-2-methyltetra-hydropyran.10... 

Pd/P(t-Bu)., in the presence of Cy2NMe, is an unusually mild and versatile catalyst for Heck reactions of aryl chlorides (Tables 1 and 2) (as well as for room-temperature reactions of aryl bromides).21 22 23 Example A, the coupling of chlorobenzene with butyl methacrylate, illustrates the application of this method to the stereoselective synthesis of a trisubstituted olefin a-methylcinnamic acid derivatives are an important family of compounds that possess biological activity (e.g., hypolipidemic24 and antibiotic25) and serve as intermediates in the synthesis of pharmaceuticals (e.g., Sulindac, a non-steroidal anti-inflammatory drug26). Example B, the coupling of 4-chlorobenzonitrile with styrene, demonstrates that Pd/P(t-Bu). can catalyze the Heck reaction of activated aryl chlorides at room temperature. 

Ishihara K., Hattori K., Yamamoto H. Highly Stereoselective Synthesis of p-Amino Esters via Donhle Stereodifferentiation in EnantioseL Synth. fi-Amino Acids 1997 159, Ed. Juaristi E., Pb. Wiley-VCH N.Y. 

Chan T-H, Xin Y-C, von Itzstein M (1997) Synthesis of phosphonic add analogs of siaUc acids (Neu5Ac and KDN) as potential sialidase inhibitors. J Org Chem 62 3500-3504 Chand P, Kotian PL, Dehghani A, El-Kattan Y, Lin T-H, Hutchison TL, Babu YS, Bantia S, Elliott AJ, Montgomery JA (2001) Systematic structure-based design and stereoselective synthesis of novel multisubstituted cyclopentane derivatives with potent antiinfluenza activity. J Med Chem 44 4379 392... 

Many chemical reactions and processes yield cationic racemic products, and either a resolution or a stereoselective synthesis must be envisaged to obtain the chiral cations in an enantioenriched or enantiopure form. Resolution has been strongly studied [130] and selected representative examples of such processes mediated by chiral P( VI) anions are presented. 

Scheme 9 Stereoselective synthesis of cw-p-menthane-l,7,8-triol (A) and cA-p-menth-8-ene-l,7-diol (B).

Enders D (1993) Stereoselective synthesis. Springer, Heidelberg, Germany, p 63... 

Giblin, G.M.P., Jones, C.D., Simpkins, N.S. (1997) A Concise Stereoselective Synthesis of Epi-batidine Employing Conjugate Addition to an Alkenyl Sulfone Intermediate as the Key Step. Syniett, 589-590. 

There can be significant differences in the rates of elimination of the stereoiso-meric (3-hydroxysilanes. Van Vranken and co-workers took advantage of such a situation to achieve a highly stereoselective synthesis of a styryl terpene. (The lithiated reactant is prepared by reductive lithiation see p. 625). The syn adduct decomposes rapidly at -78° C but because of steric effects, the anti isomer remains unreacted. Acidification then promotes anti elimination to the desired /i-isomer.275... 

Jackson and coworkers have used a new approach to the synthesis of P-hydroxy-a-amino acids using (arylthio)nitrooxiranes. D-Isopropylideneglyceraldehyde is converted into the corresponding 1-arylthio-l-nitroalkene, which is a key material for stereoselective synthesis of P,y-dihydroxyamino acids (Scheme 4.6). The key step is stereoselective nucleophilic epoxida-tion of the 1-arylthio-l-nitroalkene. Syn and anti epoxides are selectively obtained by appropriate choice of epoxidation reagent.51... 

The stereoselective synthesis of awri-P-amino-a-hydroxy acid derivatives using nucleophilic epoxidation of 1-arytlthio-l-nitroalkenes has been reported (Eq. 4.41).54... 

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