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The syntheses of the enantiomerically pure, carnitine-related /?-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 carbony1 carbon, the /?-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)-carKeywords asymmetric ring-opening -carnitinecyclizations /?-lactones * nucleophilic substitutions

Chemoselective conversion of both the carbonyl group and the carbon bearing the nitro group, of 2-nitro ketones, into two methylenes is performed in one pot, under mild conditions.

1 in practically quantitative yield (720 mg, > 99 "h). 6: A solution of 5 (1.5 g, 4.47 mmol) in H,O was transferred onto Amberlite IRA-402 (30 g. activated as HCO;) at 5'C and eluted with cold water ( 5 C) The eluate was allowed to stand for 4 h at room temperature to give, after water evaporation under vacuum, a crude product, which was taken up into CH,CN and filtered. The filtrate was evaporated to dryness to give 6 (0.855 g, XO%) as a white solid. M.p. 160°C (decomp.): [n], = -24.7 ( c = 1 in MeOH); 'H NMR (300 MHz. D,O, 25°C)-6 = 5. IH). 3.98-3.89 (m, 3H), 3.54-3.46 (dd. ' J = 16.8 HI,