Author Archives: Young-jung cho

Exploring Caffeine to Expand the Pharmaceutical World

What do the effects of the chemicals in caffeine tell us? Researchers at the University of British Columbia, led by Dr. Laurel Schafer, answers this question, in 2019, by developing an efficient method to produce a similar chemical, known to be used in various applications. 

A starting material reacts with a chemical in a determined set of conditions to yield a single product. This product identifies itself as a class of pseudoalkaloids.

Pseudoalkaloids can be described by their use for biological activity and exhibit enhanced properties compared to alkaloids, such as cancer treatment. Pharmaceutical industries often investigate biological activities of alkaloids to use them for drugs. 

If you are a coffee lover, you probably know the naturally occurring substance, caffeine, and its stimulating properties to our nervous system. Caffeine is classified as a pseudoalkaloid.

Using a special type of reaction, these alkaloids can be created with materials that are compatible with each other. Past studies can be improved to target specific types of pseudoalkaloids by changing the materials and methods used.

Pseudoalkaloids can be artificially made, but time-consuming multiple synthetic steps limit the production of  pseudoalkaloids. Importantly, the challenge lies in the reactivity of the starting materials, and whether it can react to produce the desired pseudoalkaloid without byproducts. 

This proves to be a challenge because structurally complex or large chemicals have a hard time to mingle with their pairs. As such, this gives rise to multiple unwanted products, as seen in similar studies.

The solution lies within the tantalum catalyst, a tool that speeds up and controls the reaction, which is tested on a reaction to observe its effectiveness on producing the final product. Existing studies experimented with different types of metal catalysts and show a high potential for great results.

An idea was proposed to add molecules that bind to the tantalum catalyst. This binding molecule improves the reactivity of the catalyst and proceeds the reaction, thereby converting as much initial material as possible to the final product.

After many attempts of finding the perfect combination of chemicals to react in the optimal conditions, Dr. Laurel Schafer’s group has synthesized the desired pseudoalkaloid of interest. For public use, the product is isolated and purified easily, since the reactivity of the reaction is maximized.

The experiment is deemed successful as it tackled all the problems faced from past researchers. One example is the selectivity of the reaction, where the reaction conditions can structurally change the final product and display undesired applications.

Evidence proves the benefits of developing pseudoalkaloids, like caffeine, and hold significant demand in the public. It is possible to design synthetic methods to produce different pseudoalkaloids with caffeine in mind. 

 

 Reference

Dipucchio RC, Rosca SC, Athavan G, Schafer LL. Exploiting Natural Complexity: Synthetic Terpenoid‐Alkaloids by Regioselective and Diastereoselective Hydroaminoalkylation Catalysis. ChemCatChem. 2019;11(16):3871–6.

-Group 9 (Wilson, Young, Rachel)

 

Magical Materials Revolutionize the Pharmaceutical World

What if there’s more to caffeine than meets the eye? What if we can chemically change the way caffeine works to create a better version of itself. 

If you are a coffee lover, you probably know the naturally occurring substance, caffeine, and its stimulating properties to our nervous system. Why and how does it happen?

Using a special type of reaction, the biological activity of caffeine can be transformed to suit a variety of different applications. Past studies can be improved by changing the materials needed and the methods used. 

Dr. Schafer’s team, at the University of British Columbia, examines an approach to synthesize pseudoalkaloids (Fig. 1), chemicals present in caffeine, with great accuracy.

Figure 1. Examples of pseudoalkaloids. The pseudoalkaloids on the left are produced naturally or synthetically. The pseudoalkaloids on the right are the researchers’ target molecules. (molecules were drawn with ChemDraw 19.0; Credits: Wilson, Young, and Rachel)

Pseudoalkaloids can be artificially made, but time-consuming multiple synthetic steps limit the production of  pseudoalkaloids. Importantly, the challenge lies in the reactivity of the starting materials, and whether it can react to produce the desired pseudoalkaloid without byproducts. 

Similar studies show different products have formed, which proves to be a problem. 

Existing studies experimented with different types of metal catalysts showing potential improvement for the results. A tantalum catalyst, a tool that speeds up the reaction, is tested on a reaction to observe its effectiveness on producing the final product. 

An idea was proposed to add molecules that bind to the tantalum catalyst. This binding molecule improves the reactivity of the catalyst, thereby converting as many initial materials as possible to the final product.

Of many possible starting materials, terpenes (Fig. 2) were used for the synthesis of pseudoalkaloids. In addition to the inactive alkene groups in terpenes, various chemical structures make them attractive starting substrates to explore a new synthetic route. 

Figure 2. Examples of terpenes. Terpenes are naturally occurring organic molecules, produced by plants. The terpenes on the right are starting materials chosen by the researchers. Every terpene has unsaturated functional groups which may react with other molecules.  (molecules were drawn with ChemDraw 19.0; Credits: Wilson, Young, and Rachel)

Another key building block, an amine, can be any, as long as the nitrogen atom of an amine is directly bound to one hydrogen atom. However, a clever choice can even make the final products useful building blocks, allowing further modifications (Fig. 3)

 Figure 3. Amines with varying R groups. After reacting with a terpene, the R group of pseudoalkaloid can be further modified to form a new molecule. (molecules were drawn with ChemDraw 19.0; Credits: Wilson, Young, and Rachel)

The catalytic reaction between amines and terpenes with the tantalum catalyst showed great selectivity. Without the help of the tantalum catalyst, an amine could potentially select any active spot on a terpene and react with it, causing a mixture of pseudoalkaloids at the end of the reaction.

However, the tantalum catalyst results in one dominating product. Although the final pot contains some residual starting materials, the target pseudoalkaloids are the major product that can be easily isolated.

By constructing a pathway to ultimately arrive at the designated point, new and better options can be achieved. Caffeine is one of many that can be innovated upon.

 

Reference

Dipucchio RC, Rosca SC, Athavan G, Schafer LL. Exploiting Natural Complexity: Synthetic Terpenoid‐Alkaloids by Regioselective and Diastereoselective Hydroaminoalkylation Catalysis. ChemCatChem. 2019;11(16):3871–6.

 

-Group 9 (Wilson, Young, Rachel)

 

The magical “Ta” catalyst for pseudoalkaloids

If you are a coffee lover, you would probably know the naturally occurring substance, caffeine. But, were you aware that this substance is classified as a pseudoalkaloid?

Many pseudoalkaloids can often have biological activities like caffeine stimulates our nervous system. Ultimately, pseudoalkaloids can be used as building blocks to produce useful drugs.

In 2019, researchers at the University of British Columbia, led by Dr. Schafer, uncovered a new pathway to produce structurally simple terpenoid-alkaloids, which belong to pseudoalkaloids.

This study can be simply summarized as a reaction between a terpene and an amine with the help of a tantalum catalyst. But, let’s first explore key ingredients to deeply understand how the synthetic route works!

 

An organotantalum compound with a ureate salt
The researchers developed a catalytic reaction run by a metallic compound. Based on other known studies, they chose an organoctantalum compound to produce terpenoid-alkaloids. As like an engine is the heart of a car, the tantalum compound is an engine to drive reactions to the final products, terpenoid-alkaloids

The choice of a metallic compound is of course crucial. However, it is more important for the compound to have complete catalytic potential. How could a bare metallic compound become a complete catalyst? The answer is associating a metallic compound with a ligand such as organic molecules or salts, which can coordinate to a metal center. Of numerous possible candidates of ligands, the researchers found that a specific salt can improve the efficiency and selectivity of the bare organotantalum compound, thereby allowing it to have a complete catalytic ability.


Figure 1.The ureate salt that improved selectivity and efficiency of the organotantalum compound, Ta(CH2SiMe3)3Cl2. Of several ureate salts, the above salt was the most suitable for this study due to its solubility.

Terpenes and anilines
As the name of final products, terpenoid-alkaloids, reflects the use of terpenes, one of key ingredients is a terpene, a naturally occurring molecule. By limiting the scope of terpenes to enantiopure limonene and pinene, the types of anilines were varied and reacted with the terpenes

Now, here comes a question. What is the consequence of mixing these ingredients together?

 

Fascinating results
This study is fascinating not only for the reason that a catalytic amination of terpenes is unexplored, but also the final products are not chaotic mixtures.

What does it mean by a chaotic mixture? Some catalysts have potential to alter an intrinsic structure of a staring substance. For example, if a catalyst was able to influence the chiral center of (R)-limonene by changing its stereochemistry, a reaction batch would contain both (S) and (R)-limonenes. Consequently, the occurrence of two products is equally probable.

Also, unexplored magical ability of the tantalum catalyst in the study allows anilines to react with one specific spot of an alkene moiety in terpenes. This astonishing selectivity gives a rise to one major product.

           Figure 2.The reaction of an enantiopure limonene with six different anilines (left). The reaction of an enantiopure pinene with six different anilines (right). Both reactions result in high regio- and diastereoselectivity.

Reference
Dipucchio RC, Rosca SC, Athavan G, Schafer LL. Exploiting Natural Complexity: Synthetic Terpenoid‐Alkaloids by Regioselective and Diastereoselective Hydroaminoalkylation Catalysis. ChemCatChem. 2019;11(16):3871–6.

-Young Cho

Symmetry in a single crystal – space group frequency

If you are the one who has experience of working in a synthetic laboratory, you might come across a single crystal. Have you ever noticed that the inner structure of the crystal is arranged symmetrically?

The symmetry of molecules, atoms, or ions in a single crystal

A single crystal does not grow randomly. It grows in an ordered manner so that a particle can have three-dimensional symmetry to another particle in the crystal. The symmetry between the particles is described as a space group. Easily speaking, the space group is a way to represent the spatial pattern of molecules, atoms, or ions in a single crystal. There are 230 space groups based on group theory, and a well-defined crystal structure shows one of the space groups.

Figure 1. An example of the space group “P 1 2 1” of a SiOcrystal. The capital letter P stands for “primitive lattice”, the numbers 1 and 2 represent “1-fold and 2-fold rotation axes”, respectively. The left figure shows SiOmolecules arranged in a unit cell and the unit cell is described as the Cartesian coordinates a, b, and c. The right figure shows the same unit cell with SiOmolecules, but b axis is perpendicular to the screen. (Source: http://aflowlib.org)

Statistics of space groups

Molecules, atoms, or ions prefer to be arranged in a certain space group although they have 230 options. The database in Cambridge Crystallographic Data Centre (CCDC) contains more than one million crystal structures, and the number increases every day. The data centre reported that 986,061 structures show fully defined space groups. Interestingly, 34.4 % and 24.9 % of the structures have the space group “P 21/c” and “P -1”, respectively (Table 1). The key point is that more than 50 % of crystals, which you may come across in a laboratory, have particles arranged in either the space group P 21/c or P -1.

Table 1. Top 10 frequently occurring space groups. SG and CSD stand for space group and Cambridge structural database, respectively. (Source: CCDC, published in January 2019)

– Young Cho

Polyurethane – a chemical in your mattress

We are living in “the polymeric world”. What does it mean by the polymeric world? Look around you! We cannot keep away from the materials made up of polymers. Probably, the most common polymer exposed to our body would be a polyurethane, if you sleep on some sort of a comfortable mattress.

The use of polyurethanes

How does a mattress relate to a polyurethane?  The polyurethane is a cushioning material to produce a flexible and rigid foam. More than 50 % of polyurethanes are consumed to make the foams (Figure 1). In addition to the function of recovering an original shape, the rigidity in the range between a flexible rubber and a hard thermosetting plastic makes polyurethanes the best material for mattresses.


Figure 1. Uses of polyurethanes for various materials. Mainly, polyurethanes are used to produce foam materials. This figure is modified from the open source

The carbamate group and the backbone of polyurethanes

How could polyurethanes have rigid and flexible properties? The chemical structure of a polyurethane would explain its properties. The polyurethane is a block polymer produced from two monomers, a polyol and a diisocyanate. The reaction between hydroxyl and cyanate groups gives a rise to repeating carbamate groups in a long chain (Figure 2; left). The polar carbamate group can have intermolecular hydrogen bonding, resulting in the decrease of free volumes within a polymer system (Figure 2; right, Figure 3). Therefore, polyurethanes can have the rigid property associated with the carbamate group.

Figure 2. A chemical reaction of a diol and a diisocyanate to form a polyurethane (left). Intermolecular H-bonding of polyurethane chains (right).

Figure 3. A flexible polymer system due to a large free volume (left). A rigid polymer system due to a small free volume (right). Polyurethanes would resemble the small free volume system due to intermolecular hydrogen bonding.

The backbones of polyol and diisocyanate are also an important factor to control the flexibility of polyurethanes. The flexibility of a long hydrocarbon chain, which both or either the monomers can have, would be introduced intrinsically to the polymers. This implies that polyurethanes can be variously derivatized, switching the backbone of diols and diisocyanates.

-Young Cho

Microplastic issues? PLA can solve the problems!

Did you know that less than 11% of plastics have been recycled in Canada since the 1950s? Many plastics, such as water bottles, bags, and takeaway coffee cups, are buried in landfills and are disposed of into the oceans.

Over a long period of exposure to air, sunlight, and moisture, they eventually “disappear” – becoming invisible to the naked eye. In this case, are plastics degradable? While we may use the word “degradation”, they do not actually disappear. The invisible ones have taken the form of microplastics, thereby still existing and still polluting our ecosystem.

Video clip 1. Microplastics as a food for baby fishes.

 

To mitigate this issue, chemists have made an effort to develop biodegradable polymers that can be applied to produce commercial plastics. In modern polymer chemistry, considerable attention has been paid to polylactic acid, so-called PLA. Polylactic acid is produced from lactide which is derived from renewable resources such as corn and potato starch.

Figure 1. Chemical structures of lactide (monomer) and polylactic acid (polymer)  . ROP stands for ring-opening polymerization (a type of polymerization). DOI:10.1021/acs.accounts.7b00447

 

Unlike petroleum-based polymers used in plastics such as polyethylene (PE), polyethylene terephthalate (PET), and polypropylene (PP), PLA has biodegradability and biocompatibility.The enriched oxygen atoms in PLA and its structural flexibility make it undergo hydrolytic and enzymatic degradations, regenerating monomers and oligomers. The degraded substances are further broken down to water and carbon dioxide, precluding the formation of microplastics. Therefore, PLA is a great candidate to substitute for plastics derived from petroleum sources.

Although there are some general issues to resolve from an economical perspective, the environmentally friendly outcomes and industrial applications have made PLA a more attractive material for plastics PLA certainly has the potential to save our future!

-Young Cho

The Polymer, PLA: it will be degraded, but our future is not degraded

Did you know that less than 11% of plastics are recycled in Canada since 1950? Many plastics, such as water bottles, bags, and takeaway coffee cups, are buried in landfills and are disposed into the ocean. Over a long period of exposure to air, sunlight, and moisture, they eventually become invisible. Are they degradable? We may be able to use the word “degradation”, but they do not disappear at all. The invisible ones exist as microplastics, thereby polluting our ecosystem.

 

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Video: plastics in the ocean

To resolve the further pollution, chemists have made an effort to develop biodegradable polymers that can be applied to produce commercial plastics. In modern polymer chemistry, considerable attention has been paid to polylactic acid, so-called PLA. Polylactic acid is produced from lactide which is derived from renewable resources such as corn and potato starch.

Figure 2. Chemical structures of lactide (monomer) and polylactic acid (polymer)  . ROP stands for ring-opening polymerization (a type of polymerization). DOI:10.1021/acs.accounts.7b00447

Unlike petroleum-based polymers used in plastics, for example, polyethylene (PE), polyethylene terephthalate (PET), and polypropylene (PP), PLA has biodegradability and biocompatibility. The enriched oxygen atoms in PLA and its structural flexibility make it undergo hydrolytic and enzymatic degradations, regenerating monomers and oligomers. The degraded substances are further broken down to water and carbon dioxide, precluding the formation of micro plastics. Therefore, PLA is a great candidate to substitute for plastics derived from petroleum sources

Although there are general issues to resolve in the economical perspective, the environmentally friendly outcomes and industrial applications have made PLA more attractive research area. PLA certainly has the potential to save our future!

-Young Cho