B-D-fructofuranose (BDF) question

[dougkaye]

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Based on p. 101 in BR orgo Ch. 6: I'm curious about the numbering used for Beta-D-fructofuranose (BDF). I think it must be a typo, but I also missed a passage question about this so I want to make sure I'm clear.

1. First can someone confirm that p. 101 numbering is a typo, where the CH20H is labeled 2 and I believe it should be labeled 1.

2. Second, isn't there a convention of left to right for naming glycosidic linkages? One of the BR questions said that you could have two possible names for the linkage based on "which sugar you choose to start with". In fact, Leninger (top biochem text) says that you put the nonreducing sugar on the left and then go on to name the linkage left to right. So I don't think you can correctly use two names for the same molecule by just "reversing" the linkage.

any ideas are welcome. Thanks.

 

[attixx]

I'd love someone to clear this up as well (as I'm in the same boat as you are with TBR. Did not like how they did that section at all).

From what I've seen, all of of the reducing disaccharides/polysacharides are named left to right because the anomeric group on the left sugar is the one involved in the glycosidic bond, and that sets the naming.

Sucrose if I remember correctly is the one thats alpha-1-beta-2 (or alpha 1-2/beta 2-1 according to a question in the end of the chapter passages). I figure the difference arises because the anomeric carbon on fructose is also involved in the bond, as opposed to only one anomeric carbon involved in the bond in other disaccharides such as lactose and maltose.

There is definitely a typo in TBR and your correction is right.

TBR leaves a lot of room for confusion - all they say about fructose is "the anomeric carbon is shown at the far right in furanose rings", but then they show that picture above without numbering the carbons and don't emphasize the fact that it's the anomeric carbon that bonds.