A simple two-step approach to methyltartronic acid (2-hydroxy-2-methylpropanedioic acid, 3) from methacrylic acid (1) via α-methylglyceric acid (2) is described. It is based on the successive use of hydrogen peroxide and oxygen as oxidants in the same aqueous medium, in combination with tungstic acid and palladium on carbon as catalysts, respectively.
Photolyse von 4-Amino-, 4-Alkoxy- und 4-Hydroxy-2,3-dimethyl-1-phenyl-3-pyrazolin-5-onen
作者:Johannes Reisch、Albert Fitzek
DOI:10.1002/ardp.19763090308
日期:——
Die Photolysevon 4‐Amino‐3‐pyrazolin‐5‐onen (Typ 1) führt nach Abspaltung der Amino‐Gruppe zu 2 und 3. Das hierbei intermediär entstehende 4‐Hydroxy‐3‐pyrazolin‐5‐on 4 zerfällt im basischen Milieu zu 2 und 3; ohne Zusätze bildet es 5. Die 4‐Alkoxy‐3‐pyrazolin‐5‐one 6 bzw. 7 ergeben in methanolischer Lösung 8 bzw. 9.
Cultivation of Penicillium minioluteum with a DNA methyltransferase inhibitor led to the isolation of a novel type of aspertetronin dimer, miniolins A–C, along with their precursor. The dimeric absolute configurations were assigned by chiral HPLC and ECD calculations.
Process for preparing alkyl esters of methyltartronic acid
申请人:Istituto Guido Donegani S.p.A.
公开号:US04701550A1
公开(公告)日:1987-10-20
There is described a process for preparing alkyl esters of methyltartronic acid by hydroxylation of methacrylic acid to alpha-methylglyceric acid with H.sub.2 O.sub.2, in an aqueous medium, in the presence of H.sub.2 WO.sub.4 and optionally of H.sub.3 PO.sub.4 or H.sub.3 AsO.sub.4 or alkaline salts thereof as catalysts, at pH<2 and at temperatures of from 50.degree. to 100.degree. C., by subsequent oxidation of alpha-methylglyceric acid to methyltartronic acid with HNO.sub.3 in excess or with O.sub.2, in an aqueous-alkaline medium, in the presence of Pd or Pt carried on carbon or oxides thereof as catalysts, at temperatures of 60.degree.-100.degree. C., and final esterification of methyltartronic acid with alcohols C.sub.1 -C.sub.4.
Nucleophilic 1,2-Shifts of Alkoxycarbonyl and Carboxylate Groups in the Benzilic-Acid Type Rearrangement of ?,?-Dioxobutyric Esters
作者:Heike Gowal、L� H. Dao、Hans Dahn
DOI:10.1002/hlca.19850680121
日期:1985.2.13
high pH, the benzilic-acidrearrangement with exclusive 1,2-shift of the COO(t-Bu) group; the same is true for the corresponding isopropyl ester 1c and ethyl ester 1b at high pH, whereas at lower pH, the overall picture of these reactions is complicated by concurrent hydrolysis of the ester, followed by a 1,2-shift of the COO− group. Consequently, the shift of these electron-attracting groups cannot be