Acidic and anionic forms of 1,3-cyclic dihydroxyacetone phosphate (cDHAP) dimethyl acetal.

The six-membered cyclic phosphate diester, 5,5-dimethoxy-2-hydroxy-1,3,2-dioxaphosphorinan-2-one, C(5)H(11)O(6)P or (MeO)(2)cDHAP, which is the dimethyl acetal of cyclic dihydroxyacetone phosphate (cDHAP), has been obtained in the form of two new cyclohexylammonium (cha) salts, cyclohexylammonium 5,5-dimethoxy-2-oxo-1,3,2-dioxaphosphorinan-2-olate monohydrate, (cha)[(MeO)(2)cDHAP]·H(2)O or C(6)H(14)N(+)·C(5)H(10)O(6)P(-)·H(2)O, and cyclohexylammonium 5,5-dimethoxy-2-oxo-1,3,2-dioxaphosphorinan-2-olate, (cha)[(MeO)(2)cDHAP] or C(6)H(14)N(+)·C(5)H(10)O(6)P(-), as well as in the form of the anhydrous free acid, (MeO)(2)cDHAP. It is shown that protonation of the cyclic phosphate group influences the chair conformation of the P/O/C/C/C/O 1,3,2-dioxaphosphorinane ring, and that differences in the ring conformation correlate with different deformations observed in the ionized and protonated phosphate groups. The ring is more evenly puckered in the anions, in contrast with the flattening observed in the structure of the free acid.