The Collaborative International Dictionary of English v.0.48:

Synanthrose \Syn*an"throse"\ (s[i^]n*[a^]n"thr[=o]s), n. [From
   NL. Synantherae the Compositae; Gr. sy`n with + 'anqh`ros
   blooming.] (Chem.)
   A variety of sugar, isomeric with sucrose, found in the
   tubers of the Jerusalem artichoke (Helianthus tuberosus),
   in the dahlia, and other Compositae.
   [1913 Webster]