188 Essays in Biochemistry 



However, it was also apparent that not all polar hydroxyl groups 

 were attacked by the microorganism. Only one of the two polar groups 

 of epi-inositol (VI) had been oxidized to yield the optically active 

 D-2-keto-epi-inositol (XI), whose polar hydroxyl group in position 4 

 was resistant to further enzymatic oxidation. L-2-Keto-epi-inositol 

 (XVII), on the other hand, could be attacked by A. suboxydans, and 

 presumably converted to a diketone, as shown by the observation that 

 racemic DL-2-keto-epi-inositol (XI -+- XVII) (produced from myo- 

 inositol by oxidation with nitric acid) was oxidized with the uptake 

 of 0.5 gram atoms of oxygen per mole. 



In order to define the requirements for oxidation by A. suboxydans 

 with greater stringency, three deoxyinositols were prepared and sub- 

 jected to the action of the microorganism. 2-Deoxy-ra?/o-inositol 

 (XVIII), prepared by the catalytic reduction under acid conditions 

 of 2-keto-?m/o-inositol (X), was not attacked. DL-2-Deoxy-epi-ino- 

 sitol (XIX -f XX) , prepared in a similar manner from DL-2-keto-e7)i- 

 inositol (XI -f- XVII), was oxidized with the uptake of 0.5 gram atoms 

 of oxygen per mole. The isomer oxidized was identified as L-2-deoxy- 

 epi-inositol (XX) by the isolation of unchanged XIX from the re- 

 action mixture, as well as by the demonstration that XIX prepared 

 from D-2-keto-epi-inositol (XI) was resistant to the action of A. sub- 

 oxydans. The point of the enzymatic attack on XX was identified as 

 the polar hydroxyl group in position 4 by the reduction of the resulting 

 monoketone with sodium amalgam to 2-deoxy-m?/o-inositol (XVIII). 9 



XX XVIII A 



Inspection of the conformations of those pairs of enantiomorphs of 

 which one member only is oxidized by A. suboxydans revealed that the 

 isomers susceptible to attack all possess an equatorial hydroxyl group 

 in position d relative to the location of the oxidizable polar hydroxyl 

 group. 



