Abstract: Intermediates for transforming (2S,3S)-2-amino-3-phenyl-1,3-propanediols into their (2R,3R)-enantiomers are described. The final compounds are useful intermediates for the synthesis of antibiotics like chloramphenicol, Thiamphenicol and Florfenicol.

Abstract: Intermediates for transforming (2S,3S)-2-amino-3-phenyl-1,3-propanediols into their (2R,3R)-enantiomers are described. The final compounds are useful intermediates for the synthesis of antibiotics like Chloramphenicol, Thiamphenicol and Florfenicol.

Abstract: A four step process for transforming (2S,3S)-2-amino-3-phenyl-1,3-propanediols into their (2R,3R)-enantiomers is described. The final compounds are useful intermediates for the synthesis of antibiotics like Chloramphenicol, Thiamphenicol and Florfenicol. The starting products generally are discard products in the synthesis of said antibiotics.

Abstract: A stereoconvergent process is described for preparing optically active alpha-arylalkanoic acids using as starting substance a diastereoisomeric mixture of ketals of formula ##STR1## in which the substitutents have the meanings given in the description. The described process leads to the formation of a single enantiomer.

Abstract: A stereoselective process is described for preparing optically active alpha,beta-disubstituted carbonyl compounds, comprising forming an acetal between an alpha,beta-unsaturated aldehyde or ketone and tartaric acid or a derivative thereof, halogenating the product thus obtained, and restoring the carbonyl compound.

Abstract: A process for the preparation of the compound (2S,3S)(+)-3-hydroxy-2,3-dihydro-2-(4-methoxyphenyl)-5-(2-dimethylaminoeth yl)-1, 5-benzothiazepin-4(5H)-one is described. Said compound is an intermediate useful in the synthesis of Diltiazem.

Abstract: A stereoconvergent process is described for preparing optically active alpha-arylalkanoic acids using as starting substance a diastereoisomeric mixture of ketals of formula ##STR1## in which the substituents have the meanings given in the description. The described process leads to the formation of a single enantiomer.

Abstract: A new enantioselective process is described for preparing optically active alpha-arylalkanoic acids by:(a) halogenation on the aliphatic carbon atom alpha to the ketal group, of ketals of formula ##STR1## in which Ar represents an aryl, optionally substituted;R represents a C.sub.1 -C.sub.4 alkyl;R.sub.1 and R.sub.2, represent a hydroxy, a O.sup.- M.sup.+, OR.sub.3 or NR.sub.4 R.sub.5 group;the carbon atoms indicated by an asterisk both simultaneously are in (R) or (S) configuration.This reaction is diastereoselective, so that a mixture of alpha-haloketals is obtained in which one of the two epimers prevails, and generally strongly prevails, over the other.(b) rearrangement of the haloketals of formula ##STR2## in which X is Cl, Br or I to alpha-arylalkanoic acids in a single stage or in two successive stages, by way of esters of formula ##STR3## The compounds (A) and (C) are all new compounds. The rearrangement step (b) may be performed under new, inventive conditions.

Abstract: Compounds of formula ##STR1## wherein Ar represents an optionally substituted aryl group;R represents a C.sub.1 -C.sub.4 alkyl;R.sub.1 and R.sub.2, equal to or different from each other, represent hydroxy, O.sup.- M.sup.+, OR.sub.3 or ##STR2## group, R.sub.3 represents a C.sub.1 -C.sub.24 alkyl, a C.sub.3 -C.sub.6 cycloalkyl, a phenyl or a benzyl;M.sup.+ represents the cation of an alkaline metal;R.sub.4 and R.sub.5, equal to or different from each other, represent a hydrogen atom, a C.sub.1 -C.sub.4 alkyl, a C.sub.5 -C.sub.6 cycloalkyl, a (CH.sub.2).sub.n --CH.sub.2 OH group with n=1, 2 or 3, or R.sub.4 and R.sub.5 together are a group (CH.sub.2).sub.m with m=4 or 5, a group --CH.sub.2 --CH.sub.2 --R.sub.6 --CH.sub.2 --CH.sub.2 -- in which R.sub.6 is an oxygen atom, an N--H or N--(C.sub.1 -C.sub.

Abstract: A new enantioselective process is described for preparing optically active alpha-arylalkanoic acids by:(a) halogenation on the aliphatic carbon atom alpha to the ketal group, of ketals of formula ##STR1## in which Ar represents an aryl, optionally substituted;R represents a C.sub.1 -C.sub.4 alkyl;R.sub.1 and R.sub.2, represents a hydroxy, a O.sup.- M.sup.+, OR.sub.3 or NR.sub.4 R.sub.5 group;the carbon atoms indicated by an asterisk both simultaneously are in (R) or (S) configuration.This reaction is diastereoselective, so that a mixture of alpha-haloketals is obtained in which one of the two epimers prevails, and generally strongly prevails, over the other.(b) rearrangement of the haloketals of formula ##STR2## in which X is Cl, Br or I to alpha-arylalkanoic acids in a single stage or in two successive stages, by way of esters of formula ##STR3## The compounds (A) and (C) are all new compounds. The rearrangement step (b) may be performed under new, inventive conditions.

Abstract: A process is described for preparing optically active alpha-halogenated carbonyl compounds.This process consists of transforming the carbonyl compound into the corresponding acetal with tartaric acid or a derivative thereof, halogenating this acetal and releasing the carbonyl compound.

Abstract: A process is described for preparing alpha-haloalkyl-aryl-ketones, comprising reacting a substantially anhydrous strong acid with a ketal of formula ##STR1## in which Ar, R, R.sub.1, R.sub.2 and X have the meanings given in the description.

Abstract: Compounds of formula ##STR1## wherein Ar represents an optionally substituted aryl group;R represents a C.sub.1 -C.sub.4 alkyl;R.sub.1 and R.sub.2, equal to or different from each other, represent hydroxy, O.sup.- M.sup.+, OR.sub.3 or ##STR2## R.sub.3 represents a C.sub.1 -C.sub.24 alkyl, a C.sub.3 -C.sub.6 cycloalkyl, a phenyl or a benzyl;M.sup.+ represents the cation of an alkaline metal;R.sub.4 and R.sub.5, equal to or different from each other, represent a hydrogen atom, a C.sub.1 -C.sub.4 alkyl, a C.sub.5 -C.sub.6 cycloalkyl, a (CH.sub.2).sub.n --CH.sub.2 OH group with n=1, 2 or 3, or R.sub.4 and R.sub.5 together are a group (CH.sub.2).sub.m with m=4 or 5, a group --CH.sub.2 --CH.sub.2 --R.sub.6 --CH.sub.2 --CH.sub.2 -- in which R.sub.6 is an oxygen atom, an N--H or N--(C.sub.1 -C.sub.

Abstract: A new enantioselective process is described for preparing optically active alpha-arylalkanoic acids by:(a) halogenation on the aliphatic carbon atom alpha to the ketal group, of ketals of formula ##STR1## in which Ar represents an aryl, optionally substituted;R represents a C.sub.1 -C.sub.4 alkyl;R.sub.1 and R.sub.2, represents a hydroxy, a O.sup.- M.sup.+, OR.sub.3 or NR.sub.4 R.sub.5 group; the carbon atoms indicated by an asterisk both simultaneously are in (R) or (S) configuration.This reaction is diastereoselective, so that a misture of alpha-haloketals is obtained in which one of the two epimers prevails, and generally strongly prevails, over the other.(b) rearrangement of the haloketals of formula ##STR2## in which X is Cl, Br or I to alpha-arylalkanoic acids in a single stage or in two successive stages, by way of esters of formula ##STR3## The compounds (A) and (C) are all new compounds. The rearrangement step (b) may be performed under new, inventive conditions.