Androgens formation from cholesterol

For the formation of testosterone (51), androsten-5-3-ol-17-one (50) obtained by oxidation from cholesterol was employed although it was also derivable from diosgenin by way of l6-dehydropregnenolone as described for the preparation of progesterone. The synthesis of the androgen followed the route shown and the acetate was isolated in an overall yield of nearly 40% in the Syntex procedure from the androstenone intermediate. 

Placental synthesis of estrogens. The placenta lacks the key enzyme necessary for formation of estrogens from cholesterol (CYP 17) and relies on androgenic precursors from the maternal and fetal compartments. The major androgen used comes from the fetal zone of the fetal adrenal this is DHEAS, which is also taken up and metabolized by fetal liver into Iba-hydroxy-DHEAS. The placenta converts DHEAS into estrone (E ) and estradiol (E2) and proces.ses 16a-hydroxy-DHEAS into estriol (Ej). Estrogens enter the maternal circulation and appear in maternal urine as conjugated estrogens. 

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