Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
com-pū̆tresco (conp-), trŭi, 3, v. inch. n., to become wholly putrid, to putrefy, rot (very rare; not in Cic.): Cass. Hem. ap. Plin. 13, 13, 27, § 86; Col. 5, 10, 7; Plin. 32, 7, 23, § 67 (Sillig, conputuere).
Per tmesin: artus pereunt conque putrescunt, Lucr. 3, 343.