Cyclic phosphorochloridites (chloridates) based on chiral butane-2,3-diol and dihydrobenzoin as reagents for the analysis of enantiomeric compositions of alcohols by31P NMR spectroscopy

The use of cyclic phosphorochloridites which were prepared based on PCl₃ and chiral butane-2,3-diol or hydrobenzoin as possible reagents for the analysis of the enantiomeric composition of chiral alcohols by³¹P NMR spectroscopy is considered. The diastereomeric dispersion of chemical shifts of the resulting phosphites as well as of derived phosphates and thiophosphates is compared with that of structurally similar reagents. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 308–311, February, 2000.     

Synthesis,crystal structure,and absolute configuration of the enantiomers of chiral drug xibenolol hydrochloride

Based on the features of its crystallization, racemic 3-(2,3-dimethylphenoxy)propane-1,2-diol 2, the synthetic precursor of the chiral drug xibenolol 1, was resolved into pure enantiomers by the direct method of entrainment. The enantiomers of diol 2 through a Mitsunobu reaction were converted into the nonracemic 1,2-epoxy-3-(2,3-dimethylphenoxy)propanes (S)- and (R)-3, and then into the xibenolol enantiomers. Single crystals of (+)- and (?)-1·HCl were studied by X-ray diffraction. On the basis of the Flack parameter, the absolute (R)- and (S)-configurations were assigned to these compounds and to the other intermediate chiral substances.     

A Comparative Study of the Cyclic Chlorophosphites with C2-Symmetrical Organic Fragments as the Reagents for Enantiomeric Composition Control of the Chiral Alcohols

Abstract

The ³¹P NMR method is intensively used for enantiomeric composition control during the last years [I]. Among all other derivatizing agents the C2-symmetrical ones have some advantages.     

Lariat ethers in the chiral recognition of amino acid esters:electrospray ionization mass spectrometry investigation

The ability of the crown ethers (1–4), containing the ortho- or para- methoxyphenoxy-methyl substituents in their structure, to chiral recognition in reference to amino acid esters has been investigated by electrospray ionization mass spectrometry (ESI-MS). The method allows registering the diastereomeric complexes between the studied crowns as hosts and the protonated alanine, phenylglycine and phenylalanine methyl esters as guests in the gas phase. ESI-MS experiments using isotopically labeled guests provide robust and reproducible results, indicating a moderate degree of chiral discrimination in the series of the studied crown ethers. ESI-MS experiments using achiral amine as a reference yielded the results comparable with the previous method. It has been found that (S)-enantiomers of the crowns bind predominately (S)-enantiomers of the amino acid esters, and vice-versa. It has been shown that the chiral ortho-substituted crown (S)-1 demonstrates the more pronounced values for chiral discrimination as compared with the para-substituted crown (S)-2. This fact indicates the interrelationship between the chiral recognition and the lariat nature of crown 1. Increasing the size of the cavity and the presence of a flat aromatic moiety in crowns 3 and 4 strengthens their complexing ability, simultaneously weakening the enantioselectivity of the complexation.     

4(2)-Methoxyphenyl glycerol ethers in the synthesis of nonracemic di-O,O-acylglycerols

Effective methods for the synthesis of nonracemic 4- and 2-methoxyphenyl glycerol ethers from nonracemic 3-chloropropanediols and by direct resolution of the racemate, respectively, were developed. Some existing discrepancies related to the to chiroptical properties of their derivatives were eliminated. Both ethers were used to synthesize nonracemic 3-O-aryloxy-1,2-di-O′,O″-palmitoyl glycerols.     

Cyclic Sulfites,Key Intermediates in Synthesis of 1-Alkylamino-3-aryloxy-2-propanols from Glycidol

By treating glycidol with phenols a number of 3-aryloxypropanedioles were obtained. The latter with thionyl chloride afforded 4-aryloxymethyl-1,3,2-dioxathiolane 2-oxides. These compounds were also obtained from 4-chloromethyl-1,3,2-dioxathiolane 2-oxides by substitution aryloxy group for chlorine. The cyclic sulfides synthesized are universal intermediates in the synthesis of chiral aryloxypropanolamines among which are known -adrenoblockaders, cardiovascular drugs. From (S)-glycidol were synthesized (S)-alprenolol, (S)-propanolol, and (S)-thymolol.     

Crystallization of chiral compounds. 2. Propranolol: free base and hydrochloride

The data from IR spectroscopy, differential scanning calorimetry, and X-ray diffraction analysis are compared for crystalline specimens of homochiral and racemic propranolol and its hydrochloride. The stabilities of the racemates were quantitatively characterized and the factors responsible for the order of their stability are revealed.     

Jacobsen Enantioselective Hydrolysis of Glycidyl Diethyl Phosphate

Scalemic diethyl phosphates of glycerol and glycidol were prepared by partial enantioselective hydrolysis of racemic glycidyl diethyl phosphate in the presence of chiral Co(salen) catalyst. The enantiomeric composition of the products was analyzed by ³¹P NMR spectroscopy with organophosphorus reagents.     

Synthesis of enantiomerically pure 3-aryloxy-2-hydroxypropanoic acids,intermediate products in the synthesis of cis-4-Aminochroman-3-ols

Oxidation of accessible (R)-3-chloropropane-1,2-diol to (R)-3-chloro-2-hydroxypropanoic acid and subsequent reaction of the latter with ortho-substituted sodium phenoxide gave a number of enantiomerically pure 3-aryloxy-2-hydroxypropanoic acid which are intermediate products in the synthesis of nonracemic 4-aminochroman-3-ols.