76474-64-1

The syntheses of the enantiomerically pure, carnitine-related β-lactones 10 and 12 starting from various carnitine precursors of opposite configuration (or carnitine itself) are described. (R)-3-Chlorocarnitine (20) has also been directly prepared from (S)-carnitine (14) and has been cyclized to 12 by a second inversion of configuration of the stereogenic centre.By nucleophilic attack at the carbonyl carbon, the β-lactone carnitine derivatives have been converted into esters, amides, and guanidino congeners.Following this route, it is possible to obtain the biologically active isomer (R)-carnitine (1) starting from the otherwise useless industrial by-product (S)-carnitine (14).Nucleophilic attack by selected ambident nucleophiles at the β-carbon of the same β-lactone derivatives results in a second inversion of configuration of the stereogenic centre.Besides aminocarnitine (3), chiral acetylcarnitine (2) and acetylthiocarnitine (5) have been synthesized in homochiral forms following this latter procedure. - Keywords: asymmetric ring-opening; carnitine; cyclizations; β-lactones; nucleophilic substitutions