Subject: Arabinose structure

From: "Ibrahim M.Moustafa" <im17:at:st-andrews.ac.uk>
Date: Tue, 12 Aug 2003 17:00:56 +0100

Dear CCL users,

    I have a small question about the stereochemistry representations of 
the pyranoside structure of Arabinose.
How to draw the chair conformation of the D- and L-forms of Arabinose?.

     I'm a bit confused; if I want to draw the pyranoside chair 
conformation (4C1) of the D-form from the Fischer projection in which the 
OH at C2 lies to the left, C3(OH) to the right and C4(OH) to the right, I'd 
draw this chair conformation with:
  OH(ax) above the ring at C2, OH(ax) below the ring at C3, and OH(eq) 
below the ring at C4. Now, If I want to draw the same conformation for the 
L-form (the mirror image of D-form), do I need to alternate the OH groups 
> from axial to equatorial and vice versa? or how to draw the chair 
conformation for the L-form?

   I apologize for bothering you with this small question? I could not find 
a straight answer for my question in the textbooks of carbohydrate chemistry.

   Appreciated your help.

   regards,
   Ibrahim

Ibrahim M.Moustafa
Centre for Biomolecular Sciences
St-Andrews University
North Haugh, St-Andrews
Fife KY16 9ST
Scotland, U.K.

Tel.       +44 (0)1334 467257
Fax       +44 (0)1334 462595
e-mail:   im17:at:st-andrews.ac.uk