1559Tch24423-43811/10/052:22Page430 EQA 430 chapter 24 CARBOHYDRATES:POLYFUNCTIONAL COMPOUNDS IN NATURE ( CH2OH (w) CH-NNHC.Hs (c)( COOH -OH C=NNHC Hs HO- -H HO- -H HO- 一H -OH HO- CH2OH -OH CH-OH D-Xylitol D-Galactonic aci COOH CH2OH CH-NNHC.Hs H H 一0H C=NNHCoHs HO- H HO- H HO- -H HO- HO- H- 一OH H -OH H -OH COOH CH2OH CH2OH D-Galactaricacid p-Galactitol *Same as D-erythrose phenylosazone 41.(a)D-gulose (Figure 24-1):(b)L-allose(all OH's on left side) 42.(a)Arabinose and lyxose.Ribitol and xylitol are meso compounds (b) CH-OH CH-OH CH2OH =0 H OH HO- -H 、HO H -OH CHOH H- OH HO H -OH -OH OH -0H FCH.OH M. A new stereocenter is generated at C2.so two diastereomeric alditols are produced.In contrast. esimpler because no new stereocenter will be generated:therefore HOCH2 Also with an acetal,not a hemiacetal,at Cl(iii) (iv) (c) (i) (ii) (iii) (iv) *Same as D-erythrose phenylosazone. **Same as D-lyxose phenylosazone. ***Same as D-talose phenylosazone. 41. (a) D-gulose (Figure 24-1); (b) L-allose (all OH’s on left side) 42. (a) Arabinose and lyxose. Ribitol and xylitol are meso compounds. (b) A new stereocenter is generated at C2, so two diastereomeric alditols are produced. In contrast, reduction of any aldose will be simpler because no new stereocenter will be generated; therefore, only a single product can form. 43. (a) and (d), because they still possess hemiacetal functionality. In (b) and (c), the OH at C1 in glucose has become OCH3, and the molecule is now an acetal, incapable of mutarotation. (e) is Also with an acetal, not a hemiacetal, at C1. HOCH2 CH3 CH3 HO O HO O O D-Fructose CH2OH CH2OH O HO H H OH H OH NaBH4 CH3OH D-Glucitol CH2OH CH2OH HO H H OH H OH H OH D-Mannitol CH2OH CH2OH HO H HO H H OH H OH D-Galactose phenylosazone*** CH2OH HO H H OH NNHC6H5 CH NNHC6H5 HO H C D-Galactitol CH2OH CH2OH OH HO H HO H H OH H D-Galactaric acid COOH COOH OH HO H HO H H OH H D-Galactonic acid CH2OH COOH OH HO H HO H H OH H D-Xylose phenylosazone** CH2OH HO H H OH NNHC6H5 CH NNHC6H5 C D-Xylitol CH2OH CH2OH OH HO H H OH H 430 • Chapter 24 CARBOHYDRATES: POLYFUNCTIONAL COMPOUNDS IN NATURE 1559T_ch24_423-438 11/10/05 2:22 Page 430