Aldohexoses Ruff degradation

D-Altrose is an aldohexose. Ruff degradation of D-altrose gives the same aldopentose as does degradation of D-allose, the C3 epimer of glucose. Give the structure of D-altrose. 

Problem 22.20 Two Ruff degradations of an aldohexose give an aldotetrose that is oxidized by HNO, to /n o-tartaric acid. What can be the family configuration of the aldohexose ... 

Problem 22.28 An aldohexose (I) is oxidized by HNO, to a me o-aldaric acid (II). Ruff degradation of (I) yields (III), which is oxidized to an optically active dicarboxylic acid (IV). Ruff degradation of (III) yields (V), which is oxidized to l-( + )-tartaric acid (VI). Represent compounds (I) through (VI). M... 

The other aldohexose that gives an optically inactive aldaric acid is D-allose, with all OH groups on the right side of the Fischer projection. Ruff degradation followed by nitric acid gives an optically inactive aldaric acid, however, so X cannot be D-allose. 

Aldohexoses A and B form the same osazone. A is oxidized by nitric acid to an optically active aldaric acid, and B is oxidized to an optically inactive aldaric acid. Ruff degradation of either A or B forms aldopentose C, which is oxidized by nitric acid to an optically active aldaric acid. Ruff degradation of C forms D, which is oxidized by nitric acid to an optically active aldaric acid. Ruff degradation of D forms (-l-)-glyceraldehyde. Identify A, B, C, and D. 

The Ruff degradation and the Kiliani—Fischer synthesis allow us to place all of the aldoses into families or family trees based on their relation to D- or L-glyceraldehyde. Such a tree is constructed in Fig. 22.7 and includes the structures of the D-aldohexoses, 1-8. 

The aldohexose d-(-i-(-galactose can be obtained by hydrolysis of lactose, a disaccharide found in milk. When d-(+(-galactose is treated with nitric acid, it yields an optically inactive aldaric acid. When d-(+(-galactose is subjected to Ruff degradation, it yields d-(-(-lyxose (see Review Problem 22.15). Using only these data, write the Fischer projection formula for d-(+(-galactose. 

When subjected to a Ruff degradation, a D-aldopentose, A, is converted to an aldotetrose, B. When reduced with sodium borohydride, the aldotetrose B forms an optically active alditol. The NMR spectrum of this alditol displays only two signals. The alditol obtained by direct reduction of A with sodium borohydride is not optically active. When A is used as the starting material for a Kiliani-Fischer synthesis, two diastereomeric aldohexoses, C and D, are produced. On treatment with sodium borohydride, C leads to an alditol E, and D leads to F. The NMR spectrum of E consists of three signals that of F consists of six. Propose structures for A-F. 

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