ketose Ketonic parent sugars (polyhydroxy ketones H[CH(OH)]nC(=O)[CH(OH)]mH) and their intramolecular hemiketals. Ketonic parent sugars (polyhydroxy ketones H[CH(OH)]<small>_n</small>C(=O)[CH(OH)]<em><small>_m</small></em>H) and their intramolecular hemiketals. monosaccharide