SAR. Structure - Activity Relationships (alkoholy, amíny, aldehydy, ketóny, estery, amidy, kyseliny, uhľovodíky) 2/28/2016

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1 Structure Activity elationships (SA) identifies which functional groups are important for binding and activity SA Structure - Activity elationships (alkoholy, amíny, aldehydy, ketóny, estery, amidy, kyseliny, uhľovodíky) Method alter, remove or mask a functional group test the analogue for activity method of testing: in vitro target - trarget activity response in vitro on cells or in vivo - biological response (binding interactions with target (e.g. enzyme)) biological response (target binding pharmacokinetic properties) M-II Andrej Boháč if group is removed or modified and in vitro activity: drops or diminished => group was important for binding unaffected => group is not important onsider by analogues: 5. Structure Activity elationships (SA) modifications may disrupt binding by steric or electronic effects easiest analogues are those made directly from a lead compound 3 some analogues have to be made by a full (de novo) synthesis (e.g. replacing an aromatic ring with a heterocyclic ring) SA allows identification of important groups involved in binding SA allows identification of the pharmacophore MPIE an opioid analgesic drug DEIE antitussive drug AALGESI ATIVITY DPS 1

2 IMPTAT GUPS DETEMIED F ATIVITY MPIE 6-YMPIE ATIVITY UAFFETED MPIE AALGESI PAMAPE F PIATES 3 MPIE 3 METAZIE LEVPAL 2

3 5.1 SA on Alcohols Possible effect of analogues on binding (e.g. ether) BD Possible analogues = or BA Ether analogue 3 = or Ether analogue steric shield 3 Ether o interaction as BD o interaction as BA Ester Alkane 5.2 SA on 1 o, 2 o & 3 o Amines ( 2,, 3 ) if amine is ionised 5.2 SA on 1 o, 2 o & 3 o Amines ( 2,, 3 ) for free base -Bonding Ionic 2-2 BD = or BA -Bonding BD 2 = or 3 acts as a strong BD ote: 3 o Amines are only able to act as BA s - no hydrogen available to act as BD 3

4 5.2 SA on 1 o, 2 o & 3 o Amines ( 2,, 3 ) s of 3 o amines containing a methyl substituent s of 1 o & 2 o amines Effect on binding 2 3l Amide analogue Demethylation l 3 V-l 2 o amine 3 l 3 o amide 3 o interaction 1 o and 2 o amines are converted to 2 o and 3 o amides respectively amides cannot ionise and so ionic bonding is not possible an amide is a poor BA and so this eliminates BA interactions steric effect of acyl group is likely to hinder acting as a BD (2 o amide) PPSE A MEAISM of demetylation from nitrogen by V-l? 5.3 SA on Quaternary Ammonium Salts ( 4 ) 5.4 SA on Aldehydes and Ketones 2-3 Ionic bonding 3 d d- Induced dipole interactions s Dipole-dipole interaction BA -Bonding (= or ) s Full synthesis of 1 o -2 o amines and nitrogen to form permanent ion subsequently amides to disable ' Ketone Planar sp 2 carbon centre ab 4 or LiAl 4 ' 2 o Alcohol Tetrahedral sp 3 carbon centre 4

5 5.5 SA on Esters Effect on binding hange in stereochemistry (planar to tetrahedral) May move oxygen out of range Alcohol analogue (= or ) If still active, further reactions can be carried out on alcohol to establish importance of oxygen -bonding as BA by either oxygen s 3 a LiAl 4 ydrolysis splits molecule and may lead to a loss of activity due to loss of other functional groups - only suitable for simple esters. ydrolysis leads to a dramatic increase in polarity which may influence ability of analogue to reach target if in vivo tests are used. eduction to alcohol removes carbonyl group and can establish importance of the carbonyl oxygen, but reaction can be difficult to do if other labile functional groups are present. arboxylic acid 2 1 o Alcohol Alcohol 3 Esters are usually hydrolysed by esterases Esters are more likely to be important for pharmacokinetic reasons acting as prodrugs. 5.6 SA on Amides Prodrug Fatty Barrier Esterase BA BD Prodrug Ester masks polar groups Allows passage through fatty cell membranes Esterase (= or ) (= or ) The nitrogen of an amide cannot act as a BA - lone pair interacts with carbonyl group Tertiary amides unable to act as BD s 5

6 s ' a arboxylic acid 2 Amine ' s LiAl o Amine a / MeI 3 ' 3 o Amide ydrolysis splits molecule and may lead to loss of activity due to loss of other functional groups - only suitable for simple amides. ydrolysis leads to dramatic increase in polarity which may affect ability of analogue to reach target if in vivo tests are done eduction to amine removes carbonyl group and can establish importance of the carbonyl oxygen, but reaction may be difficult to do if other labile groups are present. -alkylation will disable BD properties of group in 2 amides. -Methylation prevents BD interaction and may introduce a steric effect that prevents also an BA interaction steric shield 3 3 o binding as BD Binding of as BA hindered 5.7 SA on arboxylic Acids as free acid as carboxylate ion BA BA BA Ionic bonding (= or ) (= or ) (= or ) (= or ) BD harged oxygen atoms are strong BA s. Group can interact by ionic and hydrogen bonding at the same time. (= or ) 6

7 5.8 SA on Aromatic ings and Alkenes Possible analogues / ' LiAl 4 ' Ester 2 Possible effects esterification prevents ionisation, BD interactions and may hinder BA by a steric effect reduction removes carbonyl oxygen as potential BA and prevents ionisation 3 2 steric shield 3 1 o Alcohol vdw hydrophobic pocket Possible analogues ' 2 / ai 2 / Pd/ ' vdw hydrophobic region o ionic bonding possible -Bonding hindered Possible effects on binding 5.10 SA of Alkyl Groups Possible interactions o fit hydrophobic pocket Buffers hydrophobic region 3 hydrophobic slot van der Waals interactions hydrophobic pocket 7

8 5.10 SA of Alkyl Groups s Easiest alkyl groups to vary are substituents on heteroatoms. Vary length and bulk of alkyl group to test space available. 3 V-l 3 Br ' ' ' ' 5.9 Miscellaneous Functional Groups in s acid chlorides - too reactive to be of used acid anhydrides - too reactive to be of used - present in anticancer drugs (alkyl. agents) -react with nucleophiles in DA Ar - commonly present (liphophilic int., fluorine F...= interactions, or halogen bond:..., bond) 2 - sometimes present but often toxic -:::- alkynes - sometimes present, but not usually important in binding interactions -S thiols - present in some drugs as important binding group to transition metals (e.g. Zn in zinc metalloproteinases MMPs) - - present in some drugs but rarely involved in binding 3 ydrolysis ' ' functional groups that may be important for electronic reasons (e.g. nitro, cyano, aryl halides) functional groups that may be important for steric reasons (e.g. alkynes) 8