Synthesis of enantiomer

Structure-based lead generation, 44 (2006) 1 Synthesis of enantiomers of drugs, 34 (1997) 203... 

A similar enzyme-catalyzed stereoselective synthesis of enantiomers of propanolamines has been recently reported30. Addition of a lipozyme from the fungus Mucor miehei to the epoxide ( )-8 in toluene and then a slightly more than one half molar equivalent of 2-propylamine gave a 29% conversion of ( )-8 to (S)-9 with an ee of 90%. For some benzene ring-substituted epoxides, both the percent conversion of the epoxide and the ee of product are slightly higher30. 

A third class of compounds that can be hydrogenated are ketones or aldehydes containing another polar group. The pressures used are high (50-100 bar H2) but the enantioselectivities are excellent. The general reaction (R can be varied extensively) is shown in Figure 4.16. Since these B-substituted ketones are easy to make, this method is extremely powerful for the synthesis of enantiomers. Furthermore, the catalyst is also very selective in the formation of diastereomers. An industrial application is shown below [19],... 

An application to the asymmetric synthesis of enantiomer-ically pure tram-hexahydroanthracen-9-ones is shown in Scheme 6. It should be possible to carry out a second stereoselective reductive alkylation of the benzoyl group in 22 as was demonstrated in the related hydrofluoren-9-one and... 

Yadav, J. S., Valli, M. Y. and Prasad, A. R. (1998). Total synthesis of enantiomers of (3Z,6Z)-cisJ), 10-epoxy 1,3,6-heneicosatriene- the pheromonal component of Diacrisia obliqua. Tetrahedron, 54, 7551-7562. 

The Synthesis of Enantiomers of Modafinil and the Asymmetric Synthesis of Armodafinil... 

Despite successes, many goals remain as yet unrealized, such as a widely applicable chiral solid catalyst for performing asymmetric synthesis of enantiomerically pure flavors, pharmaceuticals, etc. Two examples to elucidate the importance of the separate synthesis of enantiomers are limonene and asparagine while the (S)-enantiomer of limonene has citrus odour the (R)-enantiomer smells like orange while the (S)-enantiomer of asparagine has a bitter taste the (R)-enantiomer is sweet. 

Ma, D.Y, Wang, D.X., Pan, J., et al. 2008b. Nitrile biotransformations for the synthesis of enantiomer-ically enriched P -, and P -hydroxy and alkoxy acids and amides, a dramatic O-substituent effects of the substrates on enantioselectivity. Tetrahedron Asymmetry, 19 322-29. 

A novel preparation of racemic and enantiopure forms of phosphocarnitine (348) from easily available 3-chloro-2-oxopropylphosphonate (349) has been accomplished. The Baker s yeast catalysed reduction of (349) followed by kinetic resolution of the reduction product using AFl-S AMNO lipase-catalysed acylation and finally standard exchange of chlorine atom for trimethylamine group are the key steps in the synthesis of enantiomers of phosphocarnitine (Figure 56). ... 

The synthesis of enantiomers of natural products is a field of increasing interest because such compounds are used in structural studies and as probes for the elucidation of biological processes, as e.g. exemplified by the synthesis of e f-enterobactin [134]. We have reported on the synthesis of (2iS)-2-P-L-glucopyranosyloxy-4-hydroxy-7-methoxy-2//-l,4-benzoxazin-3(4//)-one (e f-GDIMBOA) starting from L-glucose and DIMBOA [135] following the method described in Fig. (18) on principle. 

Scheme 13.4 Quasi-racemic FMS of (S)- and (R)-pyridovericins. 13.2.2 Synthesis of Enantiomers of Mappicine...

Hanessian, S., Cantin, L.-D., Roy, S., Andreotti, D., and Gomtsyan, A., The synthesis of enantiomer-ically pure, symmetrically substituted cyclopropane phosphonic acids. A constrained analog of the GABA antagonist phaclophen. Tetrahedron Lett., 38, 1103, 1997. 

Figure 4.41 Synthesis of enantiomers of lardolure. Modified by permission of Shokabo Publishing Co., Ltd...

The creation of diastereoisomeric molecules which are epimeric at phosphorus presents no fundamental difficulties. Such molecules are readily available by means of reactions between the dichlorides RP(=Z)Cl2 (Z = O, S or Se) and an appropriate chiral difunctional compound. Many reactions that lead to such products were indicated in the previous chapter in connection with the synthesis of enantiomers of, particularly, (l-aminoalkyl)phos-phonic acids and related compounds. With regard to the preparation of diastereoisomeric thio- or seleno-phosphoryl compounds epimeric at phosphorus, the chiral reactants first used were modified carbohydrates and, less successfully, simple mono- or di-substituted diols. The latter provided simple monocyclic 1,3,2-dioxaphospholanes and 1,3,2-dioxaphosphorinanes which could provide (a) chiral centre(s) on (a) ring carbon atom(s), but also generated compounds epimeric at phosphorus their inconvenience often lay in lack of availability of cheap starting materials. In the case of the carbohydrates, the substrates were readily available from cheap starting materials thus, methyl 2,3-di-(9-methyl-... 

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