Hydroxocobalamin

Hydroxocobalamin is a deep-red crystalline solid that is stable both in the solid state and in solution at ambient conditions. It is readily soluble in water and dimethyl sulfoxide, less soluble in dimethylformamide, ethanol, and acetic acid, and insoluble in most other organic solvents. Its purity may be checked by optical and chromatographic techniques.1 Treatment of hydroxocobalamin with a variety of negatively charged halide and pseudohalide ligands gives the corresponding cobalamins. 

To a deaerated solution of hydroxocobalamin (25 mg, 1.8 X 10 s mole) in absolute ethanol (4 mL) in a 10-mL Erlenmeyer flask covered with a serum cap is added triethylamine (1 drop, purfied by distillation from 1-naphthyl isocyanate) followed by ethyl vinyl ether (0.16 mL, 1.5 X 10 3 mole). The red solution is allowed to stand in the dark under nitrogen until the reaction is complete (about 3 days). The reaction is followed by observing the decrease in the optical absorption at 357 nm. Fibrous red needles of the product that crystallize from solution are collected by filtration, washed with a minimum of acetone, and air dried to give 20 mg (80%). X(mH 0-KjC°3)(e) 263 (21,600), 281 (19,900), 288 (sh) (18,000), 323 (12,900), 338 (13,600), 373 (11,400), 432 (sh)(4640), 490 (sh) (6610), 525 (8420) nm. 

Recrystallization from water/acetone (even at a basic pH) causes some hydrolysis of the acetal. (2,2-Diethoxyethyl)cobalamin, like all alkyl cobalamins, is light sensitive in solution in addition, and unlike most other alkylcobalamins, it is add sensitive, decomposing to both (formylmethyl)cobalamin and aqua-cobalamin.2 The formation of other alkylcobalamins and cobaloximes by reaction with enol ethers has been described.2 

The dichloromethane (50 mL) solution of dicyanocobyrinic acid heptamethyl ester (500 mg) is placed in a 250-ml separatory funnel, and 30 mL of 30% HC104 is added. ( Caution. Perchlorates are explosive/) The mixture is shaken until the solution changes from purple to orange. The organic phase is separated from the aqueous phase and washed with water (2 X 25 mL). The dichloromethane is stripped on a rotary evaporator, yielding a dark-red solid. Yield 90%. Anal. Calcd. for CsaH NjO, CICo Co, 5.00 C, 53.94 H, 6.36 N, 5.94 Cl, 3.01. Found Co, 4.61 C, 53.26 H, 6.11 N, 6.11 C1,2.89. 

Heptamethyl aquamethylcobyrinate is obtained as a dark-red solid, solutions of which should be protected from light. Photolysis leads to homolytic cleavage of the cobalt-carbon bond, yielding the Co(III) complex in the presence of oxygen. 2iC 2 (e X KT4) 454 (0.948), 374 (0.876), 350 (0.964), 328 (1.47), 317 (1.90), 303 (2.29), and 266 (2.15) nm (see Fig. 1). The seven ester methyl groups appear between 3.52 and 3.72 ppm and the cobalt-bound methyl appears at -0.24 ppm in the H nmr spectrum (CHC13 solution, tetramethylsilane external standard). 

Trade Name Manufacturer Country Year Introducad 

Into a pressure reactor there was charged 100 ml of methanol and 1 g of diruthenium nona-carbonyl. The reactor was closed, cooled in solid carbon dioxide/acetone, and evacuated. Acetylene, to the extent of 1 mol (26 g), was metered into the cold reactor. Carbon monoxide was then pressured into this vessel at 835-9BO atmospheres, during a period of 16.5 hours while the reactor was maintained at 100°C to 1 50°C. The reactor was then cooled to room temperature and opened. 

The reaction mixture was removed from the vessel and distilled at a pressure of 30-60 mm, and a bath temperature of 30°C to 50°C until the methanol had all been removed. The extremely viscous tarry residue remaining in the still pot was given a very crude distillation, the distillate boiling at B2°C to 1 32°C/2 mm. In an attempt to purify this distillate by a more careful distillation, 5.3 g of a liquid distilling from 53°C to 150°C/5 mm was collected. At this point, much solid sublimate was noted not only in this distillate but in the condenser of the still. 7 g of the solid sublimate was scraped out of the condenser of the still. Recrystallization of the sublimate from ethyl acetate containing a small amount of petroleum ether gave beautiful crystals melting at 175°C to 177°C (5 g). Infrared analysis confirmed that this compound was hydroquinone (9% conversion). 

Chemical Name Cobinamide hydroxide phosphate 3 -ester with 5,6-dimethyl-l-o-D-ribofuranosylbenzimidazole inner salt 

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B 2 (lb)) and methylcobalamin [13422-55-4] (Ic). These, along with hydroxocobalamin [13422-51 -0] (vitamin B 2 (1 ))> die forms found in humans and other animals. Other forms of interest are iiitrocobalarnin (vitamin ( )) aquacobalamine chloride [13422-52-1] (vitamin The... 

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