asymptotally
Registered: 10/06/09
Posts: 6
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Reply with quote | #1 |
For acetal and hemiacetal disaccharides like the examples given in the Thinkbook on page 83, how do we distinguish alpha or beta structures for each monosaccharide since the former OH group that is used to classify them is now an glycoside?
Or do alpha and beta categories only apply to single monosaccharides? |
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mliou2
Registered: 10/08/09
Posts: 15
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Reply with quote | #2 |
If you flip to the next page, p. 84 in the Lecture Supplement, you'll see the example of maltose, and it has the alpha labeling. If you look carefully at the glucopyranosyl (the left one in the combined disaccharide picture), the O that is attached to the glucopyranose is trans, thereby making it a 1,4'-alpha-gluco...
So you look for the O of the OH, and look at its configuration to determine whether or not it's alpha or beta for that monosaccharide.
I hope this helps!
This also works for Lactose. If you look at the O of the OH it is axial, making it cis with the CH2OH.
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