Chemical study of the mechanism for conversion of dimethylacetal obtained by methanolysis of plasmalogen to alkenylmethylether.

The mechanism for the conversion of dimethylacetal which was obtained by methanolysis of plasmalogen to alkenylmethylether was studied by IR spectroscopy, TLC, GC-MS, 1H-NMR, and 13C-NMR. Heating dimethylacetal in an evacuated sealed glass tube at 250 degrees C for 15 min quantitatively yielded the corresponding alkenylmethylether. The alkenylmethylether yielded two bands of about equal amounts on TLC due to cis and trans configurations at the C-1 and C-2 position. Both 1H-NMR and 13C-NMR showed that the signals of protons and carbons at O-CH3, C-1, and C-2 positions were shifted downfield due to the formation of a double bond between the C-1 and C-2, and that each signal derived from O-CH3, C-1, or C-2 position was divided into two signals due to the formation of cis and trans isomers of the alkenylmethylether. As the two signals had the same intensities, it was suggested that equivalent amounts of cis and trans isomers of the alkenylmether were formed. Since alkenylmethylether was quantitatively converted from dimethylacetal, it was suggested that the alkenylether of plasmalogen could be analyzed as alkenylmethylether together with the fatty acid methylester at the same time by GLC using a silicone capillary column, OV-101.