Glycine → Citraconic acid
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[H][H].[S].NC[C:6]([OH:8])=[O:7].N[C@H:10]([C:18]([OH:20])=[O:19])[CH2:11][C:12]1C=NC=CC=1.N[C@H](C(O)=O)CS.[OH-].[Na+]>Cl>[CH3:12]/[C:11](=[CH:10]/[C:18]([OH:20])=[O:19])/[C:6]([OH:8])=[O:7][H][H].[S].NC[C:6]([OH:8])=[O:7].N[C@H:10]([C:18]([OH:20])=[O:19])[CH2:11][C:12]1C=NC=CC=1.N[C@H](C(O)=O)CS.[OH-].[Na+]>Cl>[CH3:12]/[C:11](=[CH:10]/[C:18]([OH:20])=[O:19])/[C:6]([OH:8])=[O:7]With reference to Scheme 1, Br-DMMA is reacted with Pal-cysteine to afford a Pal-cysteine thiol ether of Formula III where R1 is hydrogen, R2 is methyl, R3 is palmityl (C15H31), X is sulfur, Y is a glycine radical (—NHCH(CO2H)—), n=1 and m=1. The reaction is carried out by adding Br-DMMA (0.3 g, 0.0014 mol) directly to a suspension of Pal-cysteine in 30 ml diluted HCl at room temperature. The pH of the mixture was gradually adjusted to 7, 9 and finally 11, using 1N NaOH. The pH of the mixture was stabilized after 2 h at pH 11. After 16 h stirring at 25° C., the mixture was filtered and the filtrate acidified using 1N HCl. A white precipitate occurred which was extracted with ether. Ether was evaporated under reduced pressure. The remaining greenish oil was dried under high vacuum. 3-S-(N-Palmityl cysteinyl) methyl, 2-methyl maleic acid (420 mg, 0.84 mmol) was obtained with a melting point of 60-63° C. Molar yield was 56%.
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