W12 Chemistry of naturally occurring and synthetic sex hormones (GP)

Question 1

What are the 3 families of sex hormones?

Answer 1

Androgens, Estrogens, Progestins

• Androgens
  o Testosterone (probably the most well known) and derivatives
• Estrogens
  o estradiol and derivatives
• Progestins
  o progesterone and derivatives
• All three class of sex hormones are present in both males and females (circulating plasma level differences across gender)

Question 2

Structural features of sex hormones:

Answer 2

• They are also known as steroid hormones (created from cholesterol)
• Fused-ring structure (each ring with an identifier letter) = steroid nucleus
• Cyclopentanoperhydrophenanthrene backbone
• They have 4 rings- A,B,C,D

Question 3

Sex hormones
What are Gonanes?

Answer 3

• Functionalisation of the steroid nucleus identifies different classes of sex hormones
• Gonanes is the first family of hormones containing only the steroid nucleus and serves as the parent compound for steroids.

Gonanes: 17 carbons (backbone alone)
Estranes: 8 carbons (Methyl group on C13)
Androstanes: 19 carbons (Methyl group on C19)
Pregnanes: 21 carbons
Cholestanes: 27 carbons (Cholesterol)

Hint! Number of carbons of the central scaffold (and around it)

Question 4

Asymmetric carbons:
What does this mean?
How many asymmetric carbons are in a fully saturated steroidal nucleus?

Answer 4

• A fully saturated steroid nucleus will have specific asymmetric carbons (by definition: a carbon atom that is bonded to four different types of atoms or groups of atoms).
• In a fully saturated steroidal nucleus, there are 6 asymmetric carbons (5, 8, 9, 10, 13, 14).
• Number of possible optical isomers 26= 64.
• Atoms attached to asymmetric centers are, by convention, given the designation α if they project below the plane of the ring structure (a dashed line or hatched triangle).
• β (or a solid line or filled triangle) is given to atoms that project above the plane.

Question 5

Overview of Steroidogenesis:
What is steroidogenesis?
What is the precursor for all endogenous steroids?
What are the 3 main enzymes involved?

Answer 5

Cellular manufacture of steroid hormones
=Cholesterol

• Cytochromes P450 (CYPX) for cleavage of
  the side chain, hydroxylation, and aromatization.
• Hydroxysteroid dehydrogenases (3βHSD)
• Aromatase (CYP19A1)
  Testosterone->Estradiol

Question 6

Testosterone and derivatives

Answer 6

• Testosterone is produced by the gonads, although small quantities are also produced by the adrenal glands in both sexes.
• It is an androgen, meaning that it stimulates the development of male characteristics.
• Testosterone: most well-known androgen, binding to androgen receptors (AR).
• Dihydrotestosterone (DHT): obtained from reduction of the C4-5 double bond of testosterone. More potent AR agonist than testosterone
• Androsterone: endogenous steroid hormone, weak androgen (1/7 of testosterone potency).
  o putative pheromone o
  o generally considered to be an inactive metabolite of testosterone

Question 7

Testosterone and derivatives
What are pro-androgens?
Examples?

Answer 7

Sub-class able to bind weakly on androgen receptors until converted into testosterone.
* Chemically derived by androsterone
->Dehydroepiandrosterone (DHEA)
->Dehydroepiandrosterone sulfate (DHEA-S) carrying a sulphate group. Building block for making the male sex hormone testosterone and the female sex hormone estrogen.
* Clinical markers to check how well your adrenal glands are working.

Question 8

Estrogen derivatives:

Answer 8

• Estrone (E1) is the primary form of estrogen that female body makes after menopause.
• Estradiol (E2) is the primary form of estrogen in female body during reproductive years. It’s the most potent form of estrogen.
• Estriol (E3) is the primary form of estrogen during pregnancy. Primarily made and secreted from the placenta (with help from the fetus) about five weeks after implantation. This is also a weak estrogen
• Estetrol (E4) is only produced during pregnancy from the liver of the fetus

Question 9

Synthetic sex steroids
Why do we need them?

Answer 9

o Body not producing enough endogenous hormone
o Natural progesterone isn’t absorbed well when taken as a pill by mouth and is metabolized by the body too quickly to have much effect
* Using new formulations: Utrogestan 100mg oral capsule, derived from plants. Micronised progesterone can minimise the metabolic impact.

Question 10

Preparation of synthetic sex steroids includes making chemical modifications
on the steroid nucleus aiming to do what? (4)

Answer 10

• to enhance stability;
• to increase affinity with target receptor;
• to change pharmacokinetic properties (improve absorption, controlled
  release);
• to allow customisation for specific conditions.

Question 11

What are the uses of synthetic sex steroids? (6)

Answer 11

• Hormone-replacement therapy (menopause or andropause)
• Hormonal Contraception feminizing hormone therapy
• Treatment of Hormone-Related Disorders (e.g., Polycystic Ovary Syndrome and Endometriosis
• Gender-affirming hormone therapy
• Anti-aging skin treatment
• Oncology (breast and prostate cancer)

Question 12

Progestins – testosterone based (androstanes- 19C)
What are the examples?

Answer 12

Norethindrone acetate
Levonorgestrel
Etonogestrel
Desogestrel
Testosterone

Question 13

Progestins are …. molecules?

Answer 13

• Progestins are synthetic molecules, usually starting from a related hormone
  as an initial building block

Question 14

Progestins – progesterone based (pregnancies 21C)
what are some examples?

Answer 14

Medroxyprogesterone acetate
Progesterone
Chlormadinone acetate
Megestrol acetate
Segesterone acetate
Cyproterone acetate

Question 15

Progestins Structure-activity Relationship (SAR)
What are the features?

Answer 15

• Steroidal nucleus essential for activity
• Progestin effects but might show some androgenic activity (due to similarity
  to testosterone)
  -> Unsaturation of ring B and C increase progestin activity
  (e.g., megestrol acetate)
• Removal of methyl group on C19 -> increase progestin activity (e.g., segesterone acetate)
• C3 ketone is not essential for activity (e.g., desogestrel)
• Removal of C17 OH sharply reduces androgenic activity
  -> Less similar to testosterone
• Acetylation of C17 OH -> longer duration of action

Question 16

Spironolactone-based progestins:
What are the features?
examples?

Answer 16

• Spiro compounds are compounds that
  have at least two molecular rings sharing
  one common atom (spiro carbon)
• They have a cyclic ester= lactone
• Drospirenone
• Spirolactone
• Spironolactone - no progestogenic activity
  brand name Aldactone®
  To treat hypertension and heart failure.

Question 17

Synthetic estrogens (estranes 18C)
They are also known as..?
What are examples?

Answer 17

• Also known as exogenous estrogens (compared to endogenous estrogens
  produced by our body)

Estrogen (or estradiol)
17β-Estradiol
Ethinyl estradiol
Mestranol
Estradiol valerate

Question 18

Synthetic estrogens SAR: (for info)

Answer 18

• Natural estrogen has short duration of action due to first pass metabolism
• Mainly used for local effect on the uterus
• Synthetic estrogens differ from endogenous estrogens slightly in chemical
  structure. These slight differences cause them to be absorbed, metabolized
  (broken down), and excreted differently by the body. They also activate
  estrogen receptors differently.

Question 19

Synthetic estrogens SAR
What are the properties?

Answer 19

• Liver oxidation of OH on C17 to ketone -> Estrone (E1) -> inactive
• Solution: Addition of 17β-ethinyl blocks this oxidation making the compound orally active (e.g., ethinyl estradiol) [A]
• C17-OH stereochemistry -> 17α-estradiol is essentially inert
• Prodrug -> Estradiol valerate is rapidly metabolized to 17β-estradiol and valeric acid [B]
• Essential the distance between the two OH (C3 and C17) [C]
• C3-OH essential

Steroidal nucleus is not essential for activity

Question 20

Other synthetic estrogens?

Answer 20

• There are non-steroidal estrogens (e.g., Diethylstilbestrol - DES)
• Selective estrogen receptor modulators (SERMs)
• It’s an open-ring analogue of estradiol (the molecular dimensions of DES are almost identical to those of estradiol, particularly the distance between the terminal hydroxyl groups).
• Only the trans form (the substituents are oriented in opposite directions) is active (cis form 7% active).
• Cheap (easier chemical synthesis)
• Active as estradiol
• Longer duration of action.

also:
* Diethylstilbestrol diphosphate (Fosfestrol) - prodrug
* Dienestrol a synthetic nonsteroidal estrogen of the stilbestrol group
* Dienestrol diacetate: acetate derivative of dienestro

Question 21

Estradiol and the estrogen receptor

Answer 21

• Estrogens (natural and synthetic) are chemical messengers
• They bind to the estrogen intracellular receptor
• Important residues (in red) of the receptor interacting with the molecules.
• Essential the distance between the two OH (C3 and C17)

Hydrophobic group (steroidal nucleus or not) between the 2 OH groups making other interactions with the receptor

Question 22

Synthetic androgens: testosterone derivatives
Examples?

Answer 22

Methyltestosterone
Testosterone Nandrolone (synthetic)
Fluoxymesterone

Esters of testosterone
Testosterone propionate
Testosterone enanthate
Testosterone cypionate

Question 23

Synthetic androgens: testosterone derivatives
What is Testosterone propionate used for?

Answer 23

= Used primarily in androgen replacement therapy. It is specifically approved for the treatment of hypogonadism in men, low sexual desire, and delayed puberty in boys.

Question 24

Synthetic androgens SAR:
What are the properties?

Answer 24

• Oxygen functional groups on C3 and C17 are not essential -> 5α-Androstane still has androgenic activity [A]
• 3-ketone or 3α-OH enhances androgenic activity [B]
• 17α-position derivatives (Methyl) -> reduce first-pass metabolism -> bioavailability increase -> orally active [C].
• Long alkyl chain -> reduce activity
• Other substituents (17α-ethynyl) -> progestin-like activity
• 17-OH stereochemistry -> 17α-hydroxyl configuration (epitestosterone) has little activity
• 17β-OH Esterification -> prodrug -> increase of half-life
  (10-100min testosterone). Short ester (e.g., propionate) duration of action up to 1-2 weeks; Bulky esters (e.g., cypionate) up to 2-4 weeks [D]
• Halogenation only tolerated on C4 and C9 (e.g., fluoxymesterone)

Question 25

Hormone therapy
* Treatment with synthetic steroidal hormones can have some side effects
* Some treatments have androgenic properties (aka producing male
characteristics).

What are the alternatives?

Answer 25

• Selective Androgen Receptor Modulators (SARMs) can be used as
  alternative
• Small molecule drugs that function as either androgen receptor (AR) agonists or antagonists
• Chemical substances that mimic the effects of testosterone and anabolic steroids, with little or no side effects.

Question 26

Non-steroidal androgens
4 categories?

Answer 26

• N-arylpropionamide (A)
  -> derived from propionamide
  ➔(3 carbons, amide functional group)
  ➔N-aryl: nitrogen carrying an aromatic ring
• Bicyclic hydantoin (B)
  -> derived from hydantoin
• Tricyclic quinolines (C)
• Tetrahydroquinolines
  -> derived from quinoline (D)

Question 27

Non-steroidal androgens

Answer 27

• Most of the research is focused on N-arylpropionamide as AR agonists or
  partial agonist
• Stereochemistry -> R-isomer higher AR binding affinity vs S-isomer
• Sulfide analogs (replacement of ether oxygen with sulfur) -> greater AR
  binding affinity but hepatic oxidation -> in vivo inactivation -> reduced activity
• Heterocyclic substitution tolerated on ring B only mainly EWG groups (F, Cl,
  NO2, CN) or acetylamino substituents in para position (C4)
• Ring A with CF3 in C3 and NO2 or CN in C4

Question 28

Chemical Features of Endogenous Sex Hormones

Answer 28

Steroidal Backbone:
All endogenous sex hormones share a steroidal backbone, a cyclopentanoperhydrophenanthrene structure consisting of three cyclohexane rings (A, B, and C) and one cyclopentane ring (D).
Functional Groups:
Estrogens: Contain an aromatic A-ring with a hydroxyl group at position 3 and a keto or hydroxyl group at position 17.
Androgens: Feature a hydroxyl or keto group at position 3 and 17, and a non-aromatic A-ring.
Progestogens: Include a keto group at position 3 and 20, and often a methyl group at position 21.
Hydrophobic Nature:
The steroidal structure makes them largely hydrophobic, though they have hydroxyl and keto groups that contribute to slight hydrophilicity.
Lipophilicity:
Their lipophilicity enables them to easily diffuse through cell membranes and bind intracellular receptors.
Chirality:
The stereochemistry of these hormones is crucial for receptor binding.

Question 29

What are the key elements of the SAR of
synthetic androgens? (3)

Answer 29

• Stereochemistry
• Halogenation
• Esterification -> prodrug

Question 30

Feedback (for info)

Answer 30

17-OH stereochemistry -> 17α-hydroxyl
configuration (epitestosterone) has little
activity
* 17β-OH Esterification -> prodrug -> increase of half-life (10-100min testosterone). Short ester (e.g., propionate) duration of action up to 1-2 weeks; Bulky esters (e.g., cypionate) up to 2-4 weeks [D]
* Halogenation only tolerated on C4 and C9
(e.g., fluoxymesterone)