BIOSYNTHESIS 



239 



The condensation of 2 molecules of dipyrrylmethane A will give a 

 porphyrin I and that of a molecule of A and a molecule of B will give a 

 porphyrin of series III (in this case with the loss of one carbon in the form 

 of formaldehyde) (Fig. 64). 



d + Cz — CH3COCH2COOH + C2 



-CO2 



V 



c=c-c 



XJ 



HO 



HO 



(fy^(Sj 



Fig. 63 (Bloch) — Proposed scheme for the synthesis of cholesterol. 



Ac Pr 



/\ 



Ac Pr 



CH, 



I 

 NH, 



H 



NHjCH, H 



Pr 

 Ac 



H 

 ■C- 



Ac Pr 



13 



NH 



CHjNH, 



A ' 



Ac Pr 



Ac Pr 



CH. fi 

 NH| 



JLc-O 



H 



CH, 



I 

 NHi 



H 



"h, 



'CH.NH, 



Ac Pr 



Pr Ac 



Ac = chain of acetic acid 

 Pr = chain of propionic acid 



Fig. 64 (Shemin) — • = Ca of glycine and Cs of amino-Ievulinic acid. 



