This document specifies the requirements for (4R,6R)-6-cyanomethyl-2,2-dimethyl-1,3-dioxane-4-acetic acid tert-butyl ester (hereinafter referred to as "ATS-8") Basic requirements, requirements, test methods, inspection rules and marking, packaging, transportation and storage and quality commitments. This document applies to R-(-)-4-cyano-3-hydroxybutyric acid ethyl ester (hereinafter referred to as "ATS-5") and tert-butyl acetate as the main raw materials, through Claisen condensation reaction and carbonyl reduction ATS-8 is prepared through enzymatic catalysis and other reactions.