derivatives. The synthesis of 4-hydroxy-3-sulphonyl- oxybenzoic acid from 4-hydroxybenzoic acid is unambiguous, but that of the isomeric 3-hydroxy-.
677
BU1AkSUAL lLET
EnuHJLkLg
3-Hydroxy-4-sulphonyloxybenzoic acid Pennings & Van Kempen (1980, 1981) have used the Elbs peroxydisulphate oxidation of hydroxybenzoic acids to synthesize some sulphate esters of 3,4-dihydroxybenzoic acids required for the study of arylsulphatases and sulphotransferases Proof of structure was based only on co-chromatography with standard 3,4-dihydroxybenzoic acid derivatives. The synthesis of 4-hydroxy-3-sulphonyloxybenzoic acid from 4-hydroxybenzoic acid is unambiguous, but that of the isomeric 3-hydroxy4-sulphonyloxybenzoic acid from 3-hydroxybenozic acid is open to question since the Elbs oxidation gives substitution products both ortho and para to the phenolic group (Sethna, 1951). In fact, Forrest & Petrow (1950) carried out the oxidation of several meta-substituted phenols, including 3hydroxybenzoic acid, and reported isolation of only the 2,3- and 2,5-dihydroxy derivatives. I have repeated the oxidation of 3-hydroxybenzoic acid. The presence of all three expected isomeric dihydroxybenzoic acids was detected by paper chromatography using the techniques recommended by Smith (1969). I carried out a quantitative analysis of the products by g.l.c. after hydrolysis and trimethylsilylation; a 30m fused-silica column coated with SE-30 and a temperature gradient of IO0C/min from 150 to 250°C were used. Elution times were: 2,3-, 4.7min; 2,5-, 5.1 min; 3,4-, 5.5 min. I find that the 2,3-, 3,4-, and 2,5-isomers are produced in proportions of 1: 3: 8. Thus, the isomer claimed by Pennings & Van Kempen (1980) is indeed produced. However, the proof of structure is inadequate. In view of the predominance of other isomers in this synthesis, it is necessary to provide evidence not only that the products co-chromatograph with 3,4-dihydroxy standards, but that the corresponding 2,3- and 2,5derivatives do not. E. J. BEHRMAN Department of Biochemistry, The Ohio State University, Columbus, OH 43210, U.S.A.
(Received 2 November 1981) Vol. 201
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Forrest, J. & Petrow, V. (1950) J. Chem. Soc. 2340-2342 Pennings, E. J. M. & Van Kempen, G. M. J. (1980) Biochem. J. 191, 133-138 Pennings, E. J. M. & Van Kempen, G. M. J. (1981) Biochem.J. 193, 869-874 Sethna, S. M. (1951) Chem. Rev. 49, 91-100 Smith, I. (1969) Chromatographic and Electrophoretic Techniques, vol. 1, 3rd edn., chapter 16, Interscience, New York 0306-3275/82/030677-01$01 .50/1 (© 1982 The Biochemical Society
3-Hydroxy-4-sulphonyloxybenzoic acid We thank Dr. Behrman (Behrman, 1982) for his results that peroxydisulphate oxidation of 3hydroxybenzoic acid gives rise to all three expected isomers and for elucidation of the ratio in which they are produced. His findings are correct and are in agreement with our own results, which were, however, not presented in our paper (Pennings & Van Kempen, 1980). The three isomers were separated from each other by DEAE-Sephadex A-25 chromatography as described in that paper. In our opinion, however, the proof of the structure of 3-hydroxy-4-sulphonyloxybenzoic acid is adequate. We stated that, upon acid hydrolysis, only one product appeared, at the expense of starting material, which co-chromatographed with authentic 3,4-dihydroxybenzoic acid. As 2,3-dihydroxybenzoic acid and 2,5-dihydroxybenzoic acid have retention times differing from that of 3,4-dihydroxybenzoic acid under the h.p.l.c. conditions used (this was verified, but not stated explicitly in our paper), this implies that 3-hydroxy-4-sulphonyloxybenzoic acid indeed was the sulphate ester obtained after DEAE-Sephadex A-25 chromatography. E. J. M. PENNINGS & G. M. J. VAN KEMPEN Department of Biochemistry, Psychiatric Institute Endegeest, 2342 AJ Oegstgeest, The Netherlands (Received 20 November 1981)
Behrman, E. J. (1982) Biochem. J. 201, 677 Pennings, E. J. M. & Van Kempen, G. M. J. (1980) Biochem. J. 191, 133-138 0306-3275/82/030677-01$01.50/1 (© 1982 The Biochemical Society
