How can you tell whether a carbohydrate is in the "L" or "D" configuration?

[mr chievous]

This one is D-glucose and D-ribose. How can you tell it's D with haworth projections? Fischer projections are pretty straightforward.

---

Members don't see this ad.

 

[nabilesmail]

From what I understand, if the CH2OH group is pointing up that is a D-sugar =]

 

[mr chievous]

From what I understand, if the CH2OH group is pointing up that is a D-sugar =]

Are you sure about that? Is it really that simple?

 

[Hexon]

i think you have to draw the fischer projections and see

but unless someone knows a shortcut, i'm all ears

 

[MedPR]

.

 

[nabilesmail]

Are you sure about that? Is it really that simple?

From my notes yup. I would follow that rule UNLESS the picture looks weird with the c-o-c bond in the front or something akward like that.

If the image looks standard except for that, I would use that tip

 

[mr chievous]

From my notes yup. I would follow that rule UNLESS the picture looks weird with the c-o-c bond in the front or something akward like that.

If the image looks standard except for that, I would use that tip

MedPR, any thoughts? This is fas376 by the way - wanted to remain anonymous during the application season.

 

[NonTraditional3]

Here's a tip for fischer/haworth projection conversion: If it were LEFT UP to me, I would DOWN RIGHT (insert action here)

 

[balambfishie]

From what I understand, if the CH2OH group is pointing up that is a D-sugar =]

My notes say the same. Also, if there is no CH2OH at the last C in the ring, if the last OH is pointing down, it's also a D-sugar.

 

[gentlebeast]

Correct me if I made mistakes.
From TBR, to convert to Fischer, you go by rule "up left, down right"
So the second last carbon is on the right.
I just remembered from my class that if the second last carbon is on the right, it is D.

 

[NonTraditional3]

For a noncyclical sugar, Counting from the aldehyde, go to the highest numbered chiral carbon - draw the fischer projection - if the OH group points to the right, its a D sugar. If it points to the left, its an L.

 

[karafox]

D-sugar: -CH2OH is above the ring on the carbon to the left of oxygen.
L-sugar: -CH2OH is below "..."