A Convenient Route to Large-Scale Chemical Synthesis of p-Hydroxyphenylacetaldehyde Oxime and Its p-β-d-Glucopyranoside: Key Intermediates and Products in Plant Specialized Metabolism

Oximes are unrecognized chameleons in general and specialized plant metabolism. E- and Z-p-hydroxyphenylacetaldehyde oxime are key intermediates in the biosynthesis of the cyanogenic glucoside dhurrin produced in sorghum. Nevertheless, none of the geometrical oxime isomers accumulate in the plant. Herein, we report a convenient route to the chemical synthesis of E- and Z-p-hydroxyphenylacetaldehyde oxime and its biologically produced p-β-d-glucopyranoside using p-hydroxyphenylacetic acid as a starting material. This starting material is also available in radiolabeled forms. All reaction steps proceeded with excellent yield under mild conditions, operational facility, and scalability.