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464 Chapter 24 CARBOHYDRATES: POLYFUNCTIONAL COMPOUNDS IN NATURE CHO H OH } You now know these H OH carbons are R in sugars B, A. and H OH D-sedoheptulose as well. CH₂OH D-Ribose Next, (iv) tells you that CHO COOH COOH CHOH CHOH This carbon HO must be S H H-C-OH HNO3. H₂O. H-C-OH H OH H-C-OH H-C-OH H OH H-C-OH H-C-OH H OH CH₂OH COOH COOH Aldohexose B This is said to be Otherwise the product optically active would be meso From this information. you now can work backward toward the unknown: The stereocenters in D-sedoheptulose must be 3S, 4R, 5R. and 6R. CH₂OH HO H H OH H OH H OH CH₂OH D-Sedoheptulose 50. No. Kiliani-Fischer telongation does not alter the stereocenters in the starting material. The two pairs of products of Kiliani-Fischer elongations of any two aldoses will differ at the same stereocenters as did the starting materials. Thus they will be diastereomers of one another. By way of illustration. refer to Figure 24-1. All the aldoses in each horizontal row are diasteromers of one another. The Kiliani-Fischer converts an aldose in one row into the two aldoses immediately below it. No two aldoses in one row the pentoses) give the same aldose (hexose) in the next. 51. Refer to Figure 24-1. Ruff degradation converts an aldose in one row to the aldose immediately above it. (a) Galactose and talose both give lyxose (gulose gives xylose): (b) gulose and idose both give xylose (glucose gives arabinose): (c) allose and altrose both give ribose (mannose gives arabinose).