alpha glycosidic

[echoyjeff222]

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been trying to find the answer to this on the forums and i'm getting confused ...

can i just think of the linkages as

alpha-glycosidic linkage: below the plane glycosidic bond

beta: above the plane

Also, in sucrose, is the beta referring to the anomeric oxygen and the CH2OH that is BELOW the plane (the very right CH2OH) -- thus that is cis, thus beta?

 

[BerkReviewTeach]

Cis and trans is the better way to view it, as you have done with the very complicated sucrose example.

 

[Czarcasm]

been trying to find the answer to this on the forums and i'm getting confused ...

can i just think of the linkages as

alpha-glycosidic linkage: below the plane glycosidic bond

beta: above the plane

Also, in sucrose, is the beta referring to the anomeric oxygen and the CH2OH that is BELOW the plane (the very right CH2OH) -- thus that is cis, thus beta?

Alpha and Beta refer to the orientation of the anomeric carbon with respect to the -CH2OH group. When they are oriented trans to one another, they are alpha. When they are oriented cis to one another, they are beta. Also, you would only use alpha or beta to describe an anomeric carbon, hence why sucrose is an a-(1,2)-b linkage. In sucrose, the anomer of the glucose molecule is alpha with respect to -CH2OH; the anomer is carbon 1. This is bound to fructose, and it's anomeric carbon is beta to -CH2OH and is located on carbon 2. So collectively, it's an alpha-1,2-beta linkage.