A convenient preparation of aldonohydroxamic acids in water and crystal structure of l-erythronohydroxamic acid

Hydroxamic acids derived from aldonic acids, namely aldonohydroxamic acids, have become an increasingly important class of inhibitors of enzymes involved in the metabolism of carbohydrates. We now report the straightforward preparation of various types of aldonohydroxamic acids by a new methodology involving the use of commercial 50% aqueous hydroxylamine as the source of the free base hydroxylamine that reacts directly with the corresponding aldonolactone dissolved in water. The reaction proceeds almost instantaneously in water at room temperature, yielding generally pure products in quantitative yield. To date, this methodology is probably the most facile and efficient way to synthesize aldonohydroxamic acids. We also determined by X-ray diffraction analysis the first crystal structure of a free aldonohydroxamic acid reported to date. Crystals of l-erythronohydroxamic acid belonged to the monoclinic system, space group P21, a=5.511(3), b=7.556(1), c=8.071(3) Å, β=109.10°, and Z=2.