CHEMICAL STRUCTURE 



make to the understanding of biological phenomena is now 

 becoming increasingly apparent. Because of the widening 

 scope of biochemical experimentation, the theorist can no longer 

 afford to speculate in an experimental vacuum and hence must 

 proceed with greater restraint. On the other hand, the bio- 

 chemist, though traditionally an empiricist, has learned to accept 

 the view that the reactions he is dealing with are those of organic 

 chemistry, if of a special kind. He is therefore becoming more 

 receptive to the guidance which chemical theory can provide. 



SQUALENE 

 ROBINSON 1934 



CAROTENE 

 BRYANT 1935 



c- ^c- 

 I i 

 c. x. 



c ^c 



C I 



! I 



..c — c 



Oleic Acid 



c--cc:^ 



9 MOLS OF TRIOSE 

 REICHSTEIN r938 



CI VETONE 

 Wl N DAUS 1933 



Fig. 1 . Eady hypotheses on cholesterol biogenesis. 



Many examples can be cited to illustrate the increasing 

 degree of coordination between structural work in organic 

 chemistry and experimentation in biochemistry, but few are as 

 instructive as the example of steroid biogenesis. The constitution 

 of the cyclopentanoperhydrophenanthrene derivatives has stimu- 

 lated thoughts as to their biological origin for nearly thirty 

 years, and it is of more than academic interest to recall some of 

 the proposals which have been made in the past. Because of the 

 scarcity of the biochemical information then available, it is not 

 surprising that the early schemes on the origin of cholesterol 

 were purely formalistic in character and that the ideas which 



475 



