Process for the preparation of trans-3-formylbut-2-enenitrile

#The present invention relates to processes for the production of key intermediates in the synthetic pathway leading to naturally occurring cytokinins, particularly trans-zeatin and dihydrozeatin.

#Cytokinins are naturally occurring 6-substituted aminopurines, which are plant hormones known for their biological activity on plant growth. The more important of these effects are the abilities to induce cell division and regulate differentiation in excised plant tissue. Zeatin is one of the most active forms of the cytokinins.

#Owing to the difficulty in isolating even minute quantities of the naturally occurring cytokinins, researchers have turned their efforts to investigating synthetic pathways to form biologically active 6-substituted aminopurines. For trans-zeatin, much of the research has been focused on a suitable synthesis of trans-3-hydroxymethylbut-2-enylamine (VI), the highly functionalized unsaturated side chain which can be condensed, by known methods, with 6-chloropurine to form trans-zeatin. In the case of dihydrozeatin (II), the desired side chain is 3-hydroxymethylbutylamine (VII).

#FIGS. 1A and 1B are formula sheets showing structural formulas and names for the compounds referred to in the specification; and

#FIG. 2 is a reaction sheet showing an example of the reactions described in the specification.

#The present invention involves a base catalyzed condensation of a pyruvaldehyde acetal with acetonitrile to form the corresponding acetal of 3-formylbut-2-enenitrile, which is subsequently hydrolyzed in acidic conditions to form trans-3-formylbut-2-enenitrile. FIG. 2 shows the reactions involved in the present invention starting from pyruvaldehyde dimethyl acetal.

#A large number of pyruvaldehyde acetals are suitable as a starting material for the process. Generally the structural formula for the pyruvaldehyde acetal is ##STR2## where R is an alkyl, cycloalkyl, substitued alkyl or alkenyl group, having from about 1-10 carbon atoms, or R is a methylene group in a polymethylene chain --(CH.sub.2).sub.n -- in a cyclic acetal having a 5-10 membered ring structure. Thus the general formula as given is meant to represent both subtituted acetals, such as pyruvaldehyde dimethyl acetal, and cyclic acetals such as 2-acetyl-1,3-dioxan.

#A number of pyruvaldehyde acetals are commercially available, however they can also be prepared by reacting 1,3-dihydroxy-2-propanone with monohydric or dihydric alkanols by, for example, the method of S. K. Gupta, J. Org. Chem., 41, 2642, 1976.