| 摘要 |
A process is provided for the preparation of trans-3-formylbut-2-enenitrile (V), a key intermediate in the synthetic pathway leading to trans-zeatin (I) and dihydrozeatin (II), both of which are naturally occurring cytokinins. The process involves a base catalyzed condensation of a dialkyl or cyclic acetal of pyruvaldehyde (III) with acetonitrile to yield the corresponding dialkyl or cyclic acetal of 3-formylbut-2-enenitrile (IV). The reaction proceeds regioselectively to form the favored trans-isomer in good yield. The alpha , beta -unsaturated nitrile thus formed is hydrolyzed under acidic conditions to yield trans-3-formylbut-2-enenitrile (V), which can be easily distilled without contamination of the cis-isomer. The trans-3-formylbut-2-enenitrile can be selectively or exhaustively reduced to form either trans-3-hydroxymethylbut-2-enylamine (VI) or 3-hydroxymethylbutylamine (VII), which compounds can be condensed with 6-chloropurine (IX) by known methods to form trans-zeatin or dihydrozeatin respectively.
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