276 PHOTOSYNTHESIS 



From 3 d-allose and d-latose : 



H H H H 



CH2OH — C — C — C — C — CH:0 



I I I I 

 OH OH OH OH 



and 



H H H OH 



CH2OH _C — C — C — C — CH:0 



I i I I 

 OH OH OH H 



would be obtained, but these are not formed, so Nef concludes that 

 d-pseudo-fructose forms the 2-3-d-glucosendiol (2) only. This is an im- 

 portant point in the theory. 



From 4 by rearrangement a mixture of all the aldo-2-keto and 3-keto 

 hexoses would be obtained ; since this does not occur Nef concludes that 

 this endiol is not formed from d-glucose, d-mannose or d-fructose. 



An entirely analogous situation prevails in the d-galactose series. Here 

 there are possible the following endiols : 



H OH OH 



1 CHoOH — C — C — C — COH = CHOH, a-1, 2-d-galactosendiol 



I I I 

 OH H H 



H OH 



2 CHoOH — C — C — COH = COH — CH2OH, 2, 3-d-galactosendiol 



I I 

 OH H 



H OH H 



3 CHoOH — C — C — C — COH = CHOH, (5-1, 2-d-galactosendiol, 



OH H OH 



H 



4. CHoOH — C — COH = COH . *CHOH . CH.OH, 3, 4-d-galactosen- 

 I diol (2 forms) 



OH 



