BIOCHEMICALLY IMPORTANT C0M;P0UNDS IQQ 



which is not fermented by yeasts, and then ' methose ', a 

 syrup which on dilution undergoes fermentation, i.e. it 

 contains a sugar which can provide nourishment for hetero- 

 trophic organisms. E. Fischer and F. Passmore^^^ showed 

 that ' formose ' and ' methose ' contained a and /3 ' acrose ' 

 (DL-fructose and DL-sorbose). H. and A. Euler^*'* observed 

 the condensation of formaldehyde in aqueous solution in the 

 presence of calcium carbonate. In this way they obtained, 

 among a number of other products, glycolic aldehyde, which 

 was formed by the aldol condensation of two molecules of 

 formaldehyde 



HCHO + HCHO^CHoOH.CHO 



Experiments by Fischer and others^^^ showed that succes- 

 sive aldol condensations of glycolic aldehyde gave rise to 

 tetroses and hexoses. However, in their experiments the 

 Eulers found DL-araboketose, which had evidently been 

 formed by the condensation of glycolic aldehyde and glycer- 

 aldehyde. 



As E. Schmitz^^^ showed, glyceraldehyde condenses in the 

 presence of calcium or barium hydroxide to give fructose 

 and sorbose. In this reaction part of the glyceraldehyde is 

 first converted into dihydroxyacetone and this then combines 

 with the remaining glyceraldehyde to give a hexose. It was 

 later^" established that condensation of glyceraldehyde and 

 dihydroxyacetone leads to the formation of hexoses, whereas 

 condensation of glycolic aldehyde and glyceraldehyde gives 

 rise to pentoses. 



There has now accumulated in the scientific literature a 

 very large amount of material concerning the formation of 

 sugars and their derivatives in the way indicated above. ^*® 

 Such reactions have even been used for the production of 

 sugars on a technical scale. "^ 



All the conditions necessary for the spontaneous formation 

 of sugars were present in the primaeval hydrosphere — the 

 starting materials in the form of various aldehydes and 

 ketones, the catalysts in the form of lime, chalk, etc. 



Thus we have very good reason to suppose that sugars, 

 compounds which play a very important part in metabolism 

 both as sources of energy and as structural materials for living 



