TBR Bio: Sugar Config Question

[justadream]

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I'm referring to the Raffinose passage XII (page 79 in TBR Part II)

For #75, the answer is that the bond can be characterized as both:

I) alpha(1=>2) configuration
II) beta(2=>1) configuration


I understand the first configuration but I am confused about the second one.

More specifically, how do you know the second one is beta? Is it because the O on the anomeric carbon of fructose (originally an OH - it has now formed a bond with glucose) is on the same side (pointing down) as the CH2OH group on Carbon-6 (which is also pointing down)?

The explanation from TBR says "Since the bond at the anomeric carbon [of fructose] is pointing up, above the plane of the Haworth projection, it is in the Beta-configuration"

How is the bond at the anomeric carbon of fructose pointing UP? From the picture, it looks to be pointing down.

 

[pepocho]

.

 

[xbowers003]

Look on page 100 of your book at the bottom. In the bold face it states that if the anomeric carbon is CIS with respect to the last carbon (carbon number 6) then its Beta. Try not to take the literal "up" and focus on the fact that its axial versus equatorial. Since both the anomeric carbon and the last carbon (carbon number 6) are both axial, they are beta (or cis). The fructose pointing up you're referring to is in the axial position, while the last carbon is in the equatorial position, making them "trans" or alpha.

Hope this helps. Im not the best teacher at times.