On this page, I want to talk about another transformation that monosaccharides can undergo in base. So guys, in basic conditions, monosaccharides will undergo a multitude of tautomerizations and isomerizations. This is one reason that we typically don't want to expose monosaccharides to base because you get such a mixture of isomers that it just makes a big mess out of things. The most profound of these transformations that's possible is the ability of aldoses to reversibly rearrange into ketoses in the presence of base literally making brand new monosaccharides. This process is called a bunch of different things, so we have to keep our names straight. First of all, it's simply just called an aldose-ketose rearrangement. So that's the title of this page. It's also called the anediol rearrangement, where anediol is the intermediate that's going to be used for this process. If your professor says that they want you to be able to draw the mechanism for the anediol rearrangement, this is the reaction they're talking about. Finally, it's actually also called the L'Obry-Bruijn-Van Eckenstein reaction. Yes, that's the real name. If you look on Wikipedia, that is a name for this reaction. We need to keep our names straight, but at the end of the day, that's really the hardest part. The mechanism is not as difficult as remembering the name, okay?
Before I show you the detailed mechanism, I want to show you the general reaction, so you guys can get a sense of how inefficient this type of reaction is. We're going to pick on beta-D-glucopyranose because this is a monosaccharide you should know very well by now. We've already discussed how it's possible for a beta-anomer to mutarotate to a combination of alpha and beta anomers. That's called mutarotation. We've also already discussed how it's possible in base for a monosaccharide to epimerize at the C2 position. And that's what we get here in the second product where glucopyranose turns into mannopyranose because the C2 position becomes racemized, with half of it going right and half of it going left. This is called epimerization. But finally, we also have the ability to completely rearrange glucopyranose into a furanose that's made out of a ketone. So it's possible for beta-D-glucopyranose to become defructofuranose, which is just a completely different monosaccharide, a different ring, and everything's different about it, and this happens through what we call rearrangement or what's also known as the anediol rearrangement. So, in the next video, I will show you guys the whole mechanism for how we obtain this molecule. Let's move on to the next video.
