BIOL 0280 Lecture Notes - Lecture 7: Aldehyde, Stereoisomerism, Ketone
7 Nov 2016
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Document Summary
All naturally occurring sugars are in the d configuration (hydroxy group on the right) Assigned to the c most distant from the oxidized c. Numbering starts most proximal to the oxidized carbon (c=o, c with more multiply bonded o) Molecule with n chiral centers can have 2^n possible stereoisomers. The chiral center most distant from the carbonyl c defines d- and l-forms. C=o at end of molecule with an h. The ones that occur in nature tend to be thermodynamically stable in cyclic form. 1 3c, 2 4c, 8 5c, 8 6c aldoses. 1 3c, 1 4c, 2 5c, 4 6c. In a cyclized sugar, with a oh group at each c, thermodynamic stability driven by sterics (equitorial positioning of substituents) --> why glucose is so common. Epimers: two sugars differ only in the configuration around one c atom (special type of diastereomer) (special type of diastereomer) D-mannose and d-galactose are both epimers of d-glucose.
