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Acetyl-D,L-thiolcarnitine was synthesized by the acid-catalyzed addition of thiolacetic acid to 4trimethylammonio-2-butenoic acid. AcetyI-D,L-thiolcarnitinc was the precursor of D,L-thiolcarnitine. which was preparcd by base hydrolysis. -I-hiolcarnitine significantly enriched in thc L-isomer was prepared from acetyI-D,L-thiolcarnitine using carnitine acetyltransferase as the resolving agent. The C2, C~ and C,, carnitine thiolesters were obtained by acylating thiolcarnitine with the corresponding N-hydroxysuccinimide esters. As a substrate for carnitine acetyltransferase, acetylthiolcarnitine gave the same kinetic constants as did acetylcarnitine; on the other hand, thiolcarnitine and carnitine gave the same K,o but the V ..... with thiolcarnitine was less than 5% of the value obtained with carnitine. With thiolcarnitine and acetyhhiolcarnitine as reactants, the measured K,q, at 30 C and pH 7.0, for the reacti~)n catalyzed by carnitine acetyhransferase (see below) was 4.6_+. I. acetylthiolcarnitine+ CoA --acetyI-CoA + thiolcarnitinc Lipids 18: 382-386, }983.A published abstract ( 1 ), appearing in 1970, stated that a long-chain carnitine thiolester was biologically active as an analog of the corresponding carnitine ester. Thiolcarnitine (i.e., 4-trimethylammonio-3-mercaptobutanoate) attracted our attention because its availability would allow us to synthesize affinity labels and photoaffinity labels for carnitine and carnitine ester binding sites by derivatizing the thiol group, just as we have done with CoA (2-4). We therefore developed a synthesis for thiolcarnitine and its thiolesters and evaluated their biological activity rather extensively. As we were completing these experiments, Ferri et al. (5) published a note on the mitochondrial handling of D,L-thiolcarnitine and acetyI-D,L-thiolcarnitine, thereby establishing that thiolcarnitine is indeed biologically active as a substitute for carnitine.This communication reports a synthetic route to thiolcarnitine and its thioIesters that is relatively simple, uses reagents and equipment that are commonly found in biochemical laboratories and yields products in amounts suitable for most biochemical studies. A procedure for enriching the L-isomer content of thiolcarnitine (to 77-86%) was also developed. A synthesis of thiolcarnitine has not been published previously. Preliminary reports of our experiments have appeared (6,7).

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We find that the procedure for "Sugar Dehydration without Sulfuric Acid: No More Choking Fumes in the Classroom!" (1), which calls for igniting a reaction mixture of 25 g sugar, 12 mL ethanol, and 5 g KClO 3 on a watch glass resting upon paper toweling, can lead to watch glass breakage and thereby a fire hazard. The watch glass breakage occurs through high temperature gradients generated by the exothermic reaction of KClO 3 with sugar. Once the watch glass breaks, the reaction mixture can ignite the paper toweling.The demonstration, which combines an irreversible sugar dehydration reaction with an irreversible oxidation reaction, can be effectively and safely performed in a 3 in. clay flowerpot partially filled with sand and suspended from a ring-stand with a 3 in. iron ring. Filter paper placed over the drainage hole of the clay flowerpot prevents sand from leaking out. A large collection vessel, such as an iron pail or porcelain dish, set immediately below the flowerpot provides an extra measure of safety and collects any reaction products that leave the flowerpot.Further, we found that burning ethanol-or isopropanolsoaked sugar in the absence of KClO 3 leads to a carbonaceous product similar to that reported in ref 1 as "small black upwellings of carbon" and "that smells for the most part like burnt sugar" and discussed in ref 2. This modification demonstrates sugar dehydration without the use of KClO 3 . Therefore, disposal of any unreacted and unstable sugar-KClO 3 mixture (1) is no longer a problem.With our flowerpot demonstration setup, it was easy and safe to perform and contain the traditional, colorful, and highly exothermic sugar oxidation by KClO 3 demonstration (3). Because of the large volume of hot gases released as well as the observation that KClO 3 oxidation of sugar in the presence of sulfuric acid may yield toxic and reactive gases Cl 2 , ClO, and ClO 2 (1, 3), we recommend performing this demonstration in a fume hood. To well mixed stoichiometric amounts of sugar (~1 g) and KClO 3 (~3 g), we instantaneously (~1 s) initiated the reaction with a drop (~0.05 mL) of concentrated sulfuric acid. An alternative procedure, using a match to ignite an ethanol saturated reaction mixture, gives a one-to two-minute delay before initiating the highly exothermic sugar oxidation reaction.