ija 3 m Kislost-bazi - čnost Hammettove konstante ska ke acevt Farm Izr. prof. dr Izr. prof. dr. Marko Anderluh. Marko Anderluh 23 oktober.

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1 acevts ska kem mija 3 Farm Kislost-bazičnost Hammettove konstante Izr. prof. dr. Marko Anderluh 23. oktober 2012

2 Vpliv kislinsko bazičnih lastnosti Vezava na tarčno mesto farmakodinamsko delovanje Topnost/sproščanje Topnost/absorpcija Distribucija po telesu Izločanje

3 Kislost - bazičnost HA + H 2 O A + H 3 O kislina nedisociirana oblika konjugirana baza disociirana oblika B + H 2 O BH + OH baza neprotonirana oblika konjugirana kislina protonirana oblika

4 Vezava na tarčno mesto - ionizacija Kisle skupine

5 Vezava na tarčno mesto - ionizacija Bazične skupine

6 Topnost sproščanje, absorpcija Zunanjost celice M E M B R A N A H-A H-A H-A A - Ka + H + 3 O Ključna topnost/lipofilnost obenem! Notranjost celice A - Ka + H 3 O + + Receptor

7 Vpliv pka na delovanje sulfonamidov Učinkovina MIC x 10-6 pk a (%) Sulfanilamid ,5 0,03 Sulfapiridin idi ,5 34 3,4 Sulfatiazol 4 6,8 61,4 Sulfadiazin 4 6,5 80,0

8 ph

9 pka Kaj pa je pka? Odvisnost pka ionizirana oblika?

10 Henderson-Hasselbalch pka =? ph =?

11 Foye s Principles of MC

12 pka Zakaj tako pri kislinah kot bazah operiramo s pka? ph!!!

13 1,2 1 0,8 0,6 0,4 delež A- Delež HA Monoprotična kislina pka=5 02 0, ph 1,2 1 0,8 0,6 B BH+ Monoprotična baza 0,4 02 0,2 pkb=4 pka=10 0 ph

14 Amfifilne molekule Kisle in bazične skupine se ne čutijo Neodvisna ionizacija skupin

15 1.20E E E E E E-01 Niz1 Niz2 Niz3 2.00E E ph O - O 1 NH NH 2 Amfoliti: bazična skupina pk a1 =9 kisla skupina pk a2 =4 + HO NH 2 O - NH 2 + O NH 2 O NH 2 2 3

16 1.20E E E E E-01 Niz1 Niz2 Niz3 2.00E E ph O - N Amfoliti: bazična skupina pk a1 =4 kisla skupina pk a2 =9 1 HO NH + HO N 2 3

17 Niz1 Niz2 Niz3 Amfoliti ioni dvojčki Majhna razlika v K a pk a1 =6 pk a2 = ph X Y - X Y 1 + X Y + X Y- 2 3

18 Topnostni profil sproščanje/absorpcija Kako ph odloča o absorpciji učinkovin? Kisline - absorpcija v želodcu Baze - absorpcija v tankem črevesju Okoli 3/4 učinkovin šibke baze!

19 Primera Topnostni profil sproščanje/absorpcija

20 Acidic Drug "A" - Primary absorption in the stomach Lipid Membrane Blood HA H 2 O + A - ph = 7.4 ph = 1-2 HA H 3 O + + A - Stomach Example: Aspirin - Acetylsalicylic acid CO 2 H O Water CO 2 - O + H 3 O + O CH 3 O CH 3 pka = The ph at which you have 50% unionized and 50% ionized forms of the molecule.

21 Acidic Drug "A" - Little absorption in the small intestine Lipid Membrane Blood HA H 2 O + A - ph = 7.4 ph = 8-9 HA H 2 O + A - Small intestine Example: Aspirin - Acetylsalicylic acid CO 2 H O Water CO 2 - O + H 3 O + O CH 3 O CH 3 pka = @ ph = % in ionized ph = % in ionized form

22 Basic Drug "B" - Little absorption in the stomach Lipid Membrane Blood BH+ H 2 O + B ph = 7.4 Example: Pseudoephedrine HCl ph = 1-2 BH+ H 3 O + + B Stomach HO H + Cl- NH 2 CH 3 H CH 3 Water HO H NHCH 3 H CH + HCl 3 Pseudoephedrine HCl pka= The ThepHatwhichyouhave50%unionized have unionized and 50% ionized forms of the molecule.

23 Basic Drug "B" - Primary absorption in the small intestine Lipid Membrane Blood BH+ H 2 O + B ph = 7.4 Example: Pseudoephedrine HCl ph = 8-9 BH+ H 2 O + B Small intestine HO H + Cl- NH 2 CH 3 H CH 3 Water HO H NHCH 3 H CH + HCl 3 Pseudoephedrine HCl pka = @ ph = % in ionized ph = % in ionized form

24 Topnostni profil sproščanje/absorpcija Primer: ibuprofen pka = 3,5, topnost (voda) = 0,049 mg/ml

25 Topnostni profil sproščanje/absorpcija Primer: amoksicilin pka 1 = 2,6; pka 2 = 9,6 Topnost (voda) = 3,40 g/l

26 Topnost - primer Penicilin V pka = 2,7 Kodein pka = 8,2 Stabilne soli razlika vsaj 3 enote pka

27 Ni tako preprosto...

28 Distribucija Primer: amobarbital

29 Distribucija - primer Cetirizin pka 1 = 2,2, pka 2 = 2,9, pka 3 = 8,3 Klemastin pka ~ 8

30 Distribucija - primer

31 Distribucija Plazemski proteini: Albumin (bazičen); vezava kislih spojin -kisli glikoprotein; vezava bazičnih spojin Vpliv na t1/2 in distribucijo

32 Distribucija - primer učinkovina % vezave na pka HSA Acetilsalicilna kislina 99,8 3,5 Varfarin 97 4,8 Sulfametoksazol 70 6,1 Fenobarbital ,4

33 Distribucija - primer Prime sočasne aplikacije 2 učinkovin Before Displacement After Displacement Drug A % bound % increase in unbound fraction % unbound Drug B % bound % unbound Pri učinkovinah z visokim % vezane frakcije izjemno Pri učinkovinah z visokim % vezane frakcije izjemno velike razlike!

34 Izločanje Ionizacija hidrofilne spojine lažje izločanje v urin Vezava na plazemske proteine izloča se le nevezana frakcija!

35 Predikcija kislinskih lastnosti

36 pk a vrednosti alifatskih kislin R pk a CH 3-4,74 CH 3 CH ,77 CH 3 OCH 2-3,54 CH 2 =CHCH 2-4,35 HC CCH 2-3,32 F-CH 2-2,59 Cl-CH 2-2,86 Br-CH 2-2,90 NC-CH 2-2,46 Cl 2 -CH- 1,26 Cl 3 C- 0,64 F 3 C- 0,23

37 pk a vrednosti kislin COOH X pk 2 (orto X) pk 2 (meta X) pk 2 (para X) H 420 4, , ,20 CH 3 3,91 4,27 4,38 CH 2 CH , , ,35 F 3,27 3,86 4,14 Cl 292 2, , ,97 Br 2,85 3,81 3,97 CN 314 3, , ,55 OH 2,98 4,08 4,57 OCH 3 4,09 4,09 4,47 NO 2 4,09 4,09 4,47 X

38 Hammettova enačba Hammett je opazil (1940) linearno povezanost med prosto energijo in: logaritmom relativne hitrostne konstant onstante pri hidrolizi estrov logaritmom ionizacijske ravnotežne konstante substitutiranih benzojskih kislin log (k x /k H ) = log (K x /K H ) = Za je arbitrarno določil, da je to reakcijska j, j j konstanta, ki ima za benzojsko kislino vrednost 1.

39 Disociacija benzojskih kislin pk 2 (X=H) = 4,20 G 0 = -RT logk rav = RT pk a pk 2 (X=CH 3 ) = 4,38 G 0 (R-H) = -RT log k rav (R-H) = RTpK a (R-H) G 0 (R-X) =-RT log k rav (R-X) = RTpK a (R-X) log k(r-x) = log k(r-h) + (X) pk a (R-X) = pk a (R-H) - (X) Prispevek skupine X

40 Sprememba pka pri derivatizaciji benzojske kisline Log K x K H = x Primer: COOH COOH Cl K a = 6.25x10 K a = 10.0x x10-5 Log 10.0x x10-5 = = p za Cl

41 Hammettove konstante merilo resonančnih in induktivnih vplivov; vrednost je odvisna od vrste substituenta in od pozicije na aromatskem oboču: para ali meta mesto; pri orto mestu prevlada sterični vpliv Obstajajo ustrezne konstante tudi za alifatiske spojine.

42 Hammettove konstante Elektron privlačne skupine: K x > K benzojska x = log K x log K benzojska = log (K x /K benzojska ) ima pozitivno vrednost COO- COO- X

43 Hammettove konstante Elektron donorske skupine: K benzojska > K x x = log K x log K benzojska = log (K x /K benzojska ) ima negativno vrednost COO- COO- X

44 Hammettove konstante Vpliv para substituenta na pka O O C C OH O X X + H substituent p Eq. constant log K -NH OCH CH H Cl COCH CN NO Lo og K Hammett Plot y = x R 2 = sigma p

45 Ko so (x) vrednosti znane, se uporabijo za pridobivanje informacij oobčutljivosti drugih reakcij na vplive X. Hammettova enačba K x Log ( ) K H ali k x Log ( ) = x k H Pozitivna vrednost pomeni reakcijo, kjer so elektroni odtegnjeni z mesta reakcije. Negativne vrednosti pomenijo reakc kcijo, kjer so elektroni usmerjeni k mestu reakcije.

46 Literatura predavanj Farm acevts ska kem mija 3 Foye s Principles of Medicinal Chemistry, 6. Ed. : 2. poglavje 9. poglavje G. L. Patrick: An introduction to medicinal chemistry, 4. Ed. : 18. poglavje

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