L-Ascorbic acid,5,6-O-(phenylmethylene-d)-

Originator

Zilascorb (2H) ,Norsk Hydro

Manufacturing Process

Ascorbic acid (89.2 g) was slurred in 400 ml of p-dioxane, 200 g of zinc chloride were added slowly and the resulting mixture was stirred for one hour. Next, 100 ml (104 g) of benzaldehyde were added. This reaction mixture was stirred at ambient temperature for about 24 hours and was then extracted with 500 ml of ethyl acetate. The ethyl acetate extract was itself extracted with three portions of saturated aqueous sodium chloride. The ethyl acetate solution was dried and the dried solution treated with activated charcoal and then filtered through cellulose. Concentration of the filtrate caused 5,6-O- benzylidene-L-ascorbic acid to crystallize. The above prepared compound has proven effective in treatment of various cancers of carcinoma type, but it isn't very stable and effective. The using of deuteroaldehyde improved the anticancer activity and showed greater biological activity. It has the prolonged presence in blood and could also reduce the need for frequent iv administration. This effect explains the slower reaction kinetics of compounds containing deuterium then for compounds containing hydrogen since a bond to deuterium is broken slower than a bond to hydrogen.
The deutero-5,6-O-benzylidene ascorbic acid may be prepared next way:
To 300 ml deuterated ethyl benzene (degree of deuteration: 99.4%), in which was suspended 7.6 g of 5% Pd on BaSO 4 catalyst, was added 54.7 g of freshly distilled benzoylchloride. Via a gas inlet tube, D 2 -gas was bubbled through the reaction mixture with rapid stirring. The D 2 -gas was introduced at a rate of approximately 15 L per hour. The reduction was carried out at the reflux temperature of the reaction mixture, which was 140°-145°C. After 4-5 hr reaction time all the benzoylchloride had been consumed, and the D 2 - supply was removed, and the reaction mixture cooled to room temperature. The deuterobenzaldehyde was then distilled under reduced pressure and gave 24 g of chemically pure deuterobenzaldehyde-d 1 , B.p. 74°C/22 mm Hg, n D =1.5436. Degree of deuteration: 99.4 atom % D.
56 g of deuterobenzaldehyde as above prepared are reacted with 50 g of methanol and 61 g of trimethylorthoformate in the presence of 0.8 g hydrochloric acid, while stirring the reaction mixture. After 0.5 hr reaction time at 50°C, the low boiling components of the reaction mixture were removed under vacuum, followed by distilling off the formed deuterated benzaldehyde-dimethylacetate (α,α-dimethoxy-α-d 1 -toluene). After redistilling 75 g of pure α,α-dimethoxy-α-d 1 -toluene was obtained. BP: 195°C.
40 g dry L-ascorbic acid was dissolved in 60 ml dry dimethylformamide and reacted with 41 g of deuterated-α,α-dimethoxytoluene in the presence of 300 mg p-toluene sulfonic acid. The reaction mixture was held at 60°C while continuously removing the formed methanol under reduced pressure. After the reaction had come to completion (all the calculated quantity of methanol has been removed), the DMF was distilled off under high vacuum. The oily residue was stirred with ice-cold water to obtain white crystals of deuterated-5,6-O- benzylidene ascorbic acid. The crystals can be further purified by recrystallization from benzene, but due to instability of the deuteron-5,6-O- benzylidene ascorbic acid, it is recommended that the free acid be converted to the much more stable mono-basic salt by reacting the deuteron-5,6-O- benzylidene-L-ascorbic acid with 13.5 g of sodium hydrogen carbonate in 300 ml water to obtain a clear solution of the mono-sodium salt of deutero-5,6-O- benzylidene-L-ascorbic acid.

Therapeutic Function

Antineoplastic