77?^ Role of Steroids in the Control of Mammalian Ovulation 



41 



Previously we had found 17-hydroxyprogesterone itself to be inactive as an 

 ovulation inhibitor in the rabbit (1) and, as can be seen in Fig. 7, four 

 compounds with a free 17a-hydroxyl group proved to be marginally active 

 (numbers XXXII to XXXV). Acetylation of the 17a-hydroxyl alone (XXXVI) 

 confers consistent and rather high inhibitory activity by the subcutaneous 



0=0 



Q-^ ^^ \^ XXM 

 SQ-I0,5,I 



c=s 



so !p,5,l 

 0-10 



CH, 



c=o 



0^ "^-^ \^^ XXYT 

 . so -10,2, 0.4 



Fig. 6. Miscellaneous progesterone derivatives. (Dosage in milligrams. SQ = subcutaneous 



injection ; O = by gavage.) 



route. This parallels the emergence of progestational activity with 17- 

 esterification (6). It should be noted that oral activity is not pronounced. 

 Various derivatives of 17-acetoxyprogesterone are listed in Fig. 8. Two 

 (XXXVII and XXXVIII) give evidence of minimal activity, and the two most 

 thoroughly tested (XL and XLI) are highly potent by the subcutaneous route 

 and somewhat less active when administered orally. 



In Figs. 9 through 12 are listed active compounds classified as 19-nor- 

 steroids. These are basically derivatives of 19-nortestosterone. The potent 



