Dolbier HW Solutions 609

Dolbier HW Solutions 609 - 703 CARBOHYDRATES 25.4 The...

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25.4 The con f guration at C-5 is opposite to that of D -( 1 )-glyceraldehyde. This particular carbohydrate therefore belongs to the L series. Comparing it with the Fischer projection formulas of the eight D -aldohexoses reveals it to be in the mirror image of D -( 1 )-talose; it is L -( 2 )-talose 25.5 ( b ) The Fischer projection formula of D -arabinose may be found in text Figure 25.2. The Fischer projection and the eclipsed conformation corresponding to it are Cyclic hemiacetal formation between the carbonyl group and the C-4 hydroxyl yields the a - and b -furanose forms of D -arabinose. ( c ) The mirror image of D -arabinose [from part ( b )] is L -arabinose. The C-4 atom of the eclipsed conformation of L -arabinose must be rotated 120 ° in a clock- wise sense so as to bring its hydroxyl group into the proper orientation for furanose ring
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