به نام خدا. New topics in. organic chemistry. Dr Morteza Mehrdad University of Guilan, Department of Chemistry, Rasht, Iran

Transcription

1 به نام خدا New topics in 2 organic chemistry Dr Morteza Mehrdad University of Guilan, Department of Chemistry, Rasht, Iran m-mehrdad@guilan.ac.ir

2 Combinatorial chemistry

3 history Continuous improvement in various field In 1992 Bunin & Ellman demonstrate the synthesis of 1,4-Benzodiazepine Introduce the method of generating small Non-peptide molecule i.e.peptoid First combinatorial chemistry experiment were applied to the study of Epitope In 1984 Merrifield got Nobel prize In1982 Hungarian Patent Literature published Arpad Furka,extend the Merrifield s concept In1963 Merrifield introduce the concept

4 What is combinatorial chemistry? Parallel generation of all possible combination of substituent's or components in a synthetic experiments.

5 Combinatorial Chemistry: A synthetic strategy which leads to a large set of compounds. Synthesis of many structures (diversity) Product of matrix chemistry (systematic synthesis) Automation of synthesis (speed) combinatorial technology, combinatorial library, molecular diversity

6 Why do we need Combinatorial Chemistry? 1. From New Drug discovery --- biodiversity drug design 2. From Genome Project --- post-genome Era more new drug targets

7 Difference Between Traditional Synthesis & Combinatorial Synthesis : 1 Reaction Many a times simpler Not so simple 2 Extreme condition i.e. at extreme temp./ pressure Avoid May possible to use 3 Use of highly Caustic reagent 4 Use of Inert atmosphere Generally avoid Avoid Possible to use May use 5 Multistep Reaction Avoid Possible 6 Yield of compound Gives chemical library Gives single compound

8 Techniques used in the combinatorial synthesis : solid phase Technique Solid Support Method Parallel Synthesis Manual method Automated Mixed combinatorial Synthesis Mixed & split Combinatorial Synthesis Solution phase Technique

9 ADVANTAGES Solid phase technique : Reactants are bound to a polymeric surface and modified whilst still attached. Final product is released at the end of the synthesis Specific reactants can be bound to specific beads Beads can be mixed and reacted in the same reaction vessel Products formed are distinctive for each bead and physically distinct Excess reagents can be used to drive reactions to completion Excess reagents and by products are easily removed Reaction intermediates are attached to bead and do not need to be isolated and purified Individual beads can be separated to isolate individual products Polymeric support can be regenerated and re-used after cleaving the product Automation is possible

10 REQUIREMENTS A resin bead or a functionalised surface to act as a solid support An anchor or linker A bond linking the substrate to the linker. The bond must be stable to the reaction conditions used in the synthesis A means of cleaving the product from the linker at the end Protecting groups for functional groups not involved in the synthesis

11 SUPPORTS AND LINKERS Most solid state combinatorial chemistry is conducted by using polymer beads of 10 to 750 μm in diameter. These swell in organic solvents allowing free diffusion of solvent and reagent into the interior of the bead. The polymers are inert except for the functional groups to which the molecules are attached Polystyrene resin: polystyrene with di-vinyl benzene cross linked Tenta-gel resin: polystyrene with PEG cross linked Poly acrylamide resins: Amide containing resin Ceramic/glass beads:used for high temp and pressure reactions. Linkers are usually attached because: This helps in detachment of the resin without destroying the molecule. It allows greater freedom of rotation to the molecules attached.

12 o Beads must be able to swell in the solvent used, and remain stable o Most reactions occur in the bead interior Resin bead Swelling Starting material, reagents and solvent Linkers

13 Resins are named to design the linkers..ex:-

14 Solid phase synthesis: protecting groups A few protecting groups used in solid phase synthesis. For amines. Boc ( t-butoxycarbonyl ) Fmoc (9-fluorenylmetoxy carbonyl) Tmsec (2 [ trimethylsilyl ] ethoxycarbonyl) For carboxylic acids. Tert Bu ester(t-butyl ester) Fm ester(9-fluronyl methyl ester) Tmse ester(2 [trimethylsilyl] ethyl) 14

15 = resin bead Merrifield resin for peptide synthesis (chloromethyl group) Linker Cl HO 2 C NHBoc + R H O R O H NHBoc Deprotection HO 2 C NHBoc O O NH 2 R 2 H coupling O O NH O NHBoc R H R H R 2 H O HF O aa 1 aa 2 aa 3 aa n NH 2 Release from solid support OH HO 2 C aa 1 aa 2 aa 3 aa n NH 2 Peptide

16 Wang resin O OH Linking functional group Linker Wang Resin OH Bead Linker

17 Wang resin OH Carboxylic acid + HO 2 C NH(Fmoc) O C NH(Fmoc) R H R H O piperidine deprotection O O C NH 2 R H peptide synthesis O O C aa 1 aa 2 aa 3 aa n NH 2 TFA cleavage Carboxylic acid HO 2 C aa 1 aa 2 aa 3 aa n NH 2 OH

18 Rink resin Linking functional group NH 2 O OMe Rink resin OMe Linker NH 2 Bead Linker

19 Rink resin Bead Linker Carboxylic acid NH 2 + HO 2 C R N H C O R further modifications N H C O R' cleavage TFA Primary amide H 2 N C O R'

20 Dihydropyran resin O dihydropyran derivatised resin O Linking functional group Linker Bead Linker O

21 Dihydropyran resin Alcohol ROH Bead Linker O PPts O OR further modifications O O R' TFA HO R' Alcohol

22 EQUIPMENTS USED IN SOLID PHASE

23 Parallel synthesis What is the basic idea behind parallel synthesis? The process where a single reaction product is produced in each reaction vessel.

24 To use a standard synthetic route to produce a range of analogues, with a different analogue in each reaction vessel, tube or well The identity of each structure is known Useful for producing a range of analogues optimisation or drug Approach A) Houghton's Tea bag Procedure B) Automated Parallel Synthesis

25 A) HougHton s tea BAg Procedure Each tea bag contains beads and is labelled 22 Separate reactions are carried out on each tea bag Combine tea bags for common reactions or work up procedures A single product is synthesised within each teabag Different products are formed in different teabags Economy of effort - e.g. combining tea bags for workups Cheap and possible for any lab Manual procedure and is not suitable for producing large quantities of different products

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27 B) Automated parallel synthesis Automated synthesisers are available with 42, 96 or 144 reaction vessels or wells Use beads or pins for solid phase support Reactions and work ups are carried out automatically Same synthetic route used for each vessel, but different reagents Wells Different product obtained per vessel

28 Automated parallel synthesis of all 27 tri peptides from 3 amino acids ETC

29 27 TRIPEPTIDES 27 VIALS

30 Automated parallel synthesis AUTOMATED SYNTHETIC MACHINES

31 Mixed Combinatorial Synthesis Aims To use a standard synthetic route to produce a large variety of different analogues where each reaction vessel or tube contains a mixture of products The identities of the structures in each vessel are not known with certainty Useful for finding a lead compound Capable of synthesising large numbers of compounds quickly Each mixture is tested for activity as the mixture Inactive mixtures are stored in combinatorial libraries Active mixtures are studied further to identify active component

32 Mixed combinatorial synthesis Gly Ser Ala Phe Combine Val Ala Phe Val Ser Gly Gly Ser Gly Val Gly Ala Phe Gly Gly Gly Phe Gly

33 Split & Mix Synthesis WE WILL GOT 27 TRIPEPTIDES FROM 3 VIALS, EACH TRIPEPTIDES ARE SYNTHESIZED AND FINALLY WE WILL GET ABOUT 34 MILLION PRODUCTS (1,889,568 HEXAPEPTIDES/VIAL)

34 Split & Mix Synthesis Synthesis of all possible tri-peptides using 3 amino acids

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37 MIX

38 SPLIT

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42 MIX

43 SPLIT

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47 No. of Tripeptides 9 9 9

48 No. of Tripeptides Tripeptides 3 Vials

49 TEST MIXTURES FOR ACTIVITY

50 Synthesise each tripeptide and test

51 20 AMINO ACIDS HEXAPEPTIDES etc. 34 MILLION PRODUCTS (1,889,568 hexapeptides / vial)

52 Equipment for mixed combinatorial synthesis:

53 Other methods: Multi-pin synthesis

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56 Spatial array of microchips

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58 SOLUTION PHASE SYNTHESIS

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60 Comparison between solid phase & solution phase chemistry :

61 Comparison between solid phase & solution phase technique : Sr. No. Parameter Solid Phase technique Solution phase Technique 1 Reagent Excess Optimum (unless purification done) 2 Purification Easy Can be difficult 3 Automation Easy Difficult 4 Reaction Suitable for few substance Suitable for any organic reaction 5 Scale-up Expensive Easy & inexpensive 6 Dependence of reaction development Mainly on - - support - Linkers Time