II. CHKMISTRY 



407 



2-propaiiol by lithium-aluminuni hydride reduction of Dg-lactamide and 

 isolation of the reduction product as the dibenzoate completed the proof 

 of structure. 



An extensive study has been made of the hydrolysis of vitamin B12 with 

 relation to the order of liberation and stoichiometry of the various hydro- 

 lytic fragments. On the basis of quantitative colorimetric estimation on 

 paper strip chromatograms, it has been reported that there are 2 moles of 

 l-amino-2-propanol to 1 mole of phosphorus in the vitamin B12 molecule/" 



380 <)20 460 

 WAVELENGTH IN M>i. 



Fig. 3. Absorption spectra of vitamin B12. Reproduced with permission from J. 

 Am. Chevi. Soc. 73, 355 (1951). 



4. Nature of the Cob.\lt Complex 

 Catalytic hydrogenation of vitamin B12 using platinum catalyst and hy- 

 drogen at 1 atm. caused the red color of the solution to change to dark 

 brown. Exposure to air brought about restoration of the bright-red color 

 characteristic of vitamin B12 solutions. A red crystalline product was iso- 

 lated from the reaction mixture. Examination of its physical properties 

 revealed that it was not vitamin B12 but a closely related substance which 

 was named vitamin Bi2a.^^*" Analyses revealed that the cobalt and 

 phosphorus contents were al)out the same as in vitamin B12. Several bands 

 of the absorption spectrum had changed, and the spectmm was found to 

 be more responsive to pH changes than is the spectrum of vitamin B12 

 (Figs. 1 and 3).^^ The spectrum of vitamin B^a also showed a progressive 

 change in the Slo-m^ band with time, as shown in Fig. 4.*^ ^'itamin Bi2a 

 was also isolated from culture broths of Strcptomyces griseiis*"^ and is, there- 

 fore, a naturally occurring variant of the vitamin B12 group. 



The biological activity of vitamin Bi2a has been compared with that of 

 vitamhiBi2 by various assay methods. Microbiological assays using L. lactis 



^o E. Chargaff, C. Levine, C. Green, and J. Kream, Expenentia 6, 229 (1950). 

 *' E. A. Kaczka, D. E. Wolf, and K. Folkers, J. Am. Chem. Soc. 71, 1514 (1949). 

 *■ E. A. Kaczka, R. G. Denkewalter, A Holland, and K. Folkers, J. Am. Chem,. 

 Soc. 73, 335 (1951). 



