towards synthetic protein mimics: synthesis of a new raft ... · towards synthetic protein mimics:...

Taste of Research Summer Scholarship Program

Engineering

Towards Synthetic Protein Mimics: Synthesis of a New RAFT AgentDaniel Turkovic

Dr. Jiangtao XuFundamental and Enabling Research

Background

1. RAFT Agent Synthesis

Discussion and Significance

Using the modern polymerisation technique, PET RAFTSUMI, there is potential to create synthetic moleculeswhich mimic the behaviour of proteins. Proteins consistof a sequence of amino acid monomer units, where thesequence determines the behaviour of the protein.

The technique involves the insertion of only a singlemonomer unit into a polymer chain, allowing for perfectsequence control.

Synthesis of the RAFT agent required two reactions. The first was to brominate the alcohol.The second was to add the trithiocarbonate and butyl tail.

Previous RAFT agents have had high conversion or the ability to separate diastereomers,however not both.[2]

The structural difference between these RAFT agents are their side groups (shown in green).Electron Donating (ED) groups tend to increase conversion when reacting with an ElectronWithdrawing (EW) monomer such as PMI. The bulkier side groups also tend to increase thepolarity difference between the diastereomers, allowing for separation via flashchromatography.

References1. BIOCHEMISTRY3RST. (2014). Reflection 4 - Amino Acids and Proteins Part 2. [online] Available at: https://biochemistry3rst.wordpress.com/tag/ionic-bonds/ [Accessed 27 Jan. 2019].2. Veldhuizen, N. (2018). Towards Molecular Engineering of Synthetic Peptide Mimics via RAFT polymerisation (Honours thesis)

2. PET RAFT SUMI

The PET RAFT SUMI reaction involved the addition of a Phenyl-Maleimide (PMI) monomer into thepreviously synthesised RAFT agent by irradiating with red light for 21 hours.

Objective

A key component of the technique is the RAFT agent. It is vital to develop new RAFT agents whichallow for more efficient reactions that produce purer products.In this project, a new RAFT agent, Butyl Indan Trithiocarbonate (BITC), was developed and itsefficiency in carrying out the SUMI reaction was assessed.

TEA catalystChloroform SolventStirred Overnight

Diethyl Ether Solventstirred 25min

PBr3 (0.83 mol equivalent)Overall Reaction (21 hours)

DMSO solvent

ZnTTP PhotocatalystRed Light Irradiation

1-Indanol 1-BromoindanButyl Indan Trithiocarbonate

(BITC)

(PMI)

Different diastereomers may have different chemical properties (e.g. reactivity) and physicalproperties (e.g. melting point) and thus are important to be purified for future studies in thisarea. The synthesised molecule will allow for efficient production of pure diastereomericproducts. This may prove to be essential in the ultimate goal of creating molecules to mimicthe precise nature of proteins.

BETC BATC BITC

Side Group Methyl: ED + Not bulky Ester: EW + Bulky Ring: ED + Bulky

High Conversion? 90%, 15h 28%, 33h 99%, 21h

Separable Diastereomers?

Figure 1: Amino acid sequence forming secondary structures Figure 2: BITC chemical structure

Figure 3: RAFT Agent synthesis reaction scheme

Figure 4: HNMR of 1-Indanol (Top), 1-Bromoindan (middle) and BITC (bottom)

Figure 5: PET RAFT SUMI reaction scheme

Figure 6: Flash chromatography report graph - unreacted BITC (furthermost left) and two diastereomer SUMI products (two overlapping peaks)

Figure 7: Chemical Structure of the two sets of diastereomers purified

Figure 8: HNMR of each BITC-PMI diastereomer. Noise from multiple solvents is present.

Figure 9: Chemical structures of BETC (left), BATC (middle) and BITC (right) with side groups shown in green

Table 1: Relationship between RAFT side group, conversion and SUMI product diastereomer separability.

1

12

3

45

67

8

8 234

6 + 7

DCM solvent5

2

21

34

5

6

9

8

10

10

7

1

3

4

5 67

8 + 910

13

4

5

6

9 10

10

7

8

2

10

1

238 + 9

45 7

6

1

1

1

1

Diastereomer A Diastereomer B

This resulted in the production of two sets of diastereomers which were then separated via flashchromatography.