Ch_322b_22.05

Ch_322b_22.05 - The Fischer Structural Analyses of the...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
The Fischer Structural Analyses of the Monosaccharides The Aldopentoses CHO CH 2 OH * * * There are 2 3 = 8 stereoisomers that exist as four enantiomeric pairs . The four unique stereoisomers of the D-family aldopentoses are shown below. CHO CH 2 OH OH OH OH H H H CHO CH 2 OH OH OH H H H CHO CH 2 OH OH H H H HO HO HO OH CHO CH 2 OH OH H H H HO I II III IV The D-Family Aldopentoses The names of the aldopentoses are ribose , arabinose , xylose and lyxose . Each monosaccharide has unique physical and chemical properties (mp, mps of derivatives, rotatory power). The task is to assign proper structures to each aldopentose.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chemical Information The aldopentose (-)-arabinose is oxidized by nitric acid to an optically active aldaric acid. (-)- arabinose HNO 3 H 2 O optically active aldaric acid CHO CH 2 OH * * * OH H D-family aldopentose oxidation The possible structures for the chiral aldaric acid s are: COOH COOH OH H OH H H HO COOH COOH OH H H H HO HO or This result means the partial structure of arabinose is CHO CH 2 OH * * * OH H HO H
Background image of page 2
Kiliani-Fischer Chain Extension (-)-Arabinose yields two aldohexoses, (+)-glucose and (+)-mannose , by the Kiliani-Fischer chain extension. The partial structural information for (-)-arabinose leads to the following partial structures for the two aldohexoses. CHO CH 2 OH OH H HO H partial structure for (-)-arabinose K-F CH 2 OH CHO OH H H HO OH H CH 2 OH CHO OH H H HO HO H + partial structures for (+)-glucose and (+)-mannose which are epimeric at C-2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 11

Ch_322b_22.05 - The Fischer Structural Analyses of the...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online