How are synthetic alkynes used for birth control?
Some synthetic alkynes are modifications of naturally-occurring female hormones.
Estradiol and progesterone are two naturally-occurring female hormones.
Ethinylestradiol, norethindrone, levonorgestrel, and mifepristone are four synthetic alkynes that are used in birth control pills.
Estradiol cannot be administered orally because it is rapidly oxidized by the liver.
To prevent oxidation, the 2° alcohol is converted to a 3° alcohol.
Estrone is ethynylated in one step by reaction with ethyne, sodium and sodium amide.
Ethinylestradiol prevents ovulation.
Norethindrone makes it difficult for a fertilized egg to attach to the wall of the uterus.
Levonorgestrel inhibits ovulation.
Mifepristone is often used as a "morning after" pill. If taken before ovulation, it can prevent ovulation and so prevent pregnancy.