2-methylpentanedioic acid

The two carbonyl groups in the adduct prepared from 3-methylpentanedioic acid and methyl (R)-2-thioxo-l,3-thiazolidine-4-carboxylate are diastereotopic. Reaction of the adduct with piperidine gives rise to the formation of two diastereomers 38 in a 7.4 1 ratio. The R configuration in the starting thiazolidine was known132 and the relative configuration at C-3 was determined by two methods (see pp 426 and 440). 

A mixture of 5.54 g (40 mmol) of 3-methylpentanedioic acid, 14.8 g (80 mmol) of methyl (R)-2-thioxo-4-thi-azolidinecarboxylate, 18.16 g (88 mmol) of dicyclohexylcarbodiimide, and 100 mL of pyridine is stirred at r.t. for 6 d. After evaporation of the excess solvent in vacuum, the residue obtained is treated with 150 mL of benzene, the precipitated urea is filtered off and the filtrate is condensed in vacuum to give 50 mL of solution. Flash-chromatography on a short silica gel column with benzene/ethyl acetate (10 1) affords yellow needles yield 13.0 g (70%) mp 113-114°C (ethyl acetate/diethyl ether) [a] —163.9 (c = 1.00, ethyl acetate). 

Problem 26.5 In an example of the Michael condensation, malonic ester reacts. with ethyl 2-butenoate in the presence of sodium ethoxide to yield A, of formula C13H22O6. The sequence of hydrolysis, acidification, and heating converts A into 3-methylpentanedioic acid. What is A, and how is it formed Hint See Sec. 8.20. Check your answer in Sec. 27.7.)... 

Complex ester of Sinapyl alcohol, S-10065 and 3-Hydroxy-3-methylpentanedioic acid, H-02424. Isol. from... 

Amino-3-ethylbutanedioic acid, A-70138 2-Amino-4-methylpentanedioic acid, A-60223... 

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