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SUMMARYLithium borotritide reduction of a-ionylideneacetaldehyde (2) followed by manganese dioxide oxidation provided the tritiated aldehyde (2) which retained over 95% of the label. On treatment with the ylide derived from ethyl 4-chloro-3-methylcrotonate, ethyl a-retin~ate-ll-~H (14) was obtained which, after purification, was hydrolyzed to a-retin~ic-ll-~H acid hr (15). Conversion to the methyl ester (16) followed by lithium aluminum hydride reduction yielded a l l transa-retinal (17) which was isolated as the acetate derivative (18).

The possibility of a mass spectrometric counterpart to the cyclobutanol formation which is encountered in the photolysis of carbonyl compounds has been investigated by preparing 5,5,5-[2H,]-2-methylpentanal (11) and 6,6,6-[2H,]-3-methyIhexan-2-one (111) and examining their mass spectra at high and low voltage.

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