Regulators of cell division in plant tissues. VII. The synthesis of zeatin and related 6-substituted purines

Abstract

6-(4-Hydroxy-3-methylbut-trans-2-enylamino)purine (zeatin), a cytokinin isolated from Zea mays, has been synthesized by a new route. β- Methylcrotononitrile was brominated with N-bromosuccinimide yielding γ- bromo-β-methylcrotononitrile, from which trans-γ-acetoxy-β- methylcrotononitrile was prepared. The alcohol derived from this acetate was converted into trans-β-methyl-γ-(tetrahydropyran-2- yloxy)crotononitrile. Reduction and acid hydrolysis gave 4-amino-2- methylbut-trans-2-en-1-ol which was made to react with 6-chloropurine to yield zeatin.     Several γ-alkoxy-β-methylcrotononitriles were prepared and reduced by aluminium chloride-lithium aluminium hydride to the corresponding unsaturated amines. Saturated nitrile formation also occurred in these reductions. The amines prepared were condensed with 6-chloropurine to yield a series of O-alkylzeatins. A number of other zeatin analogues were also synthesized. Two 6-methoxyalkylamino-purines were cleaved by sodium borohydride in the presence of iodine to 6-hydroxy- alkylaminopurines.