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Current time:0:00Total duration:5:24

Alpha amino acid synthesis

Video transcript

Hey so we're going to be talking about amino acid synthesis and we're just going to stick with two of the main methods for synthesizing amino acids and they both just happen to be named after old German chemist because synthesizing amino acids was probably hot stuff back in the mid to late 1800s and that the first method that we're going to be talking about is Gabriel synthesis named after Sigmund Gabriel and the second method is called Strecker synthesis so it is named after Adolf Strecker so let's start out with Gabriel synthesis first in Gabriel synthesis we begin with a molecule of what's called Thal amid Oh malonic ester ER so Anthony no malonic ester is what this molecule is called and that's kind of a mouthful so I'm just going to call this dad all righty so here's our molecule of what I'm going to call that and this is sort of the foundation upon which we're going to build our alpha amino acid and so let me draw an alpha amino acid over here to kind of remind us you know what our end product or end goal is going to be and so remember that an amino acid has first the amino group and I'm going to draw it in the protonated form and then we have our alpha carbon and then the R group or sidechain is over here and then bound to the alpha carbon is the hydrogen and a carboxylic acid group so if we come back over to our molecule fed over here we can see that the nitrogen atom is going to serve as our amino group and then we have our alpha carbon here in the center and then our carboxylic acid here is on the bottom and then we have this temporary ester group at the top so I'm going to highlight those key atoms for you here the nitrogen and the alpha carbon and then the carbonyl carbon and the reason why we start out with of these other groups attached to our key atoms is for various reasons for example RNA is prevented or quote protected from acting as a nucleophile by having the style amide group attached to it and then the carboxylic acid is protected with this ethyl ester that's attached and the alpha carbon is further activated by this additional ester group at the top now in the presence of a base and having a source of an alkyl group our molecule of fad will become alkylated to look like this so now you can see that the alkyl group here has been substituted onto the carbon atom and so this is known as the alkylated step and then the next step involves acid hydrolysis which yields this molecule and as you can see here the thala middle group was hydrolyzed along with the two esters and this is the hydrolyzed step and then finally we can add a little heat to decarboxylate this molecule or remove its carboxyl group up top here and we get our final alpha amino acid okay so this is Gabriel synthesis in a nutshell so you start out with an anthem it ohm ilanic ester and then you add a base and a source of an alkyl group and you get an alkylated amino malonic acid here and then you hydrolyze this to get your carboxylic acid group as well as your amino group then you add a little heat for decarboxylation and you wind up with the final and you know acid that's produced here and so now that we have Gabriel synthesis down let's move on to Stryker synthesis here so let's make a little room for that so next we have Strucker synthesis and the striker method is considered to be a somewhat more elegant way of synthesizing amino acids because it's really a lot more simple and efficient and just remember that simplicity is elegant and there are just three starting components and these are ammonia which serves as the precursor for our amino group potassium cyanide way serves as the precursor for the carboxylic acid group and then either an aldehyde or a ketone which serves as the scaffold on which the amino and carboxylic acid groups will be bound and this provides the carbon that will become our alpha carbon so let's take an aldehyde and react it with ammonia in the presence of an acid this will give us an amine as well as a molecule of water and then the amine can be protonated again in the presence of an acid and this time a cyanide ion will attack the protonated amine which generates an alpha amino nitrile and then finally the hydrolysis of this alpha amino nitrile yields an alpha amino acid and so there you have it Shrek or synthesis so you can see how it's a very simple and efficient and therefore elegant way of synthesizing amino acids