Epimers Diastereomers that differ

Epimers, diastereomers that differ only in a single chiral carbon that is not the reference carbon, such as D-glucose and D-galactose which differ only in -OH orientation at C-4. (e.g. D-glucose and D-galactose are epimers in C-4 Fig. 7.4) Regioisomers, which differ in the position of a substituent on the ring, as maltose and kojibiose (Fig. 7.5)... 

Epimers Diastereomers that differ in configuration at one of two or more stereo-genic units. 

Epimers (Section 25 21) Diastereomers that differ in configu ration at only one of their stereogenic centers... 

Some molecules have more than one chirality center. Enantiomers have opposite configuration at all chirality centers, whereas diastereomers have the same configuration in at least one center but opposite configurations at the others. Epimers are diastereomers that differ in configuration at only one chirality center. A compound with n chirality centers can have a maximum of 2n stereoisomers. 

Diastereomers that differ at only one chiral carbon are called epimers, ff a ring closure occurs at the epimeric carbon, two possible diastereomers may be formed. These new diastereomers are called anomers. The chiral carbon of an anomer is called the anomeric carbon, Anomers am distinguished by the orientation of their substituents. Glucose forms anomers. When the hydroxyl group on tire anomeric carbon on glucose is oriented in the opposite direction to the methyl group, the anomer is labeled ot when in the same direction, the anomer is 5. 

Two diastereomers that differ in the configuration around one stereogenic center only are called epimers. 

Extension of the carbon chain of an aldose from the carbonyl by one unit at a time can be carried out fairly readily by the Kiliani reaction. A cyanhydrin is formed by addition of cyanide ion, followed by reduction and hydrolysis (in either order) historically, the sugar was unprotected, and the cyanohydrin was hydrolysed to the sugar lactone, and then reduced with sodium amalgam (Figure 1.4). Because a new asymmetric centre is formed, two epimeric sugars result (epimers are diastereomers that differ in the configuration of only one carbon). 

All stereoisomers that are not enantiomers are termed diastereomers. For example, in a molecule containing two or more stereogenic centres any pair of stereoisomers that are not enantiomers are diastereomers. In other words, a pair of diastereomers share the same configuration at one or more, but not all, of their stereogenic centres and, unlike enantiomers, they have different physical properties. Two diastereomers that differ in configuration at only one of a number of stereogenic centres are called epimers, and their interconversion epimerization. 

Diastereomers that differ in configuration at only one asymmetric carbon are called epimers. For example, D-ribose and D-arabinose are C-2 epimers (they differ in configuration only at C-2), and o-idose and o-talose are C-3 epimers. 

Several stereochemical labels have been developed for diastereomers. Epimers are diastereomers that differ in configuration at only one of several chiral centers. The chiral center at which the difference in configuration occurs is said to be the epimeric center. Structures 69 and 70 are epimeric at C4. Anomers are epimers in the carbohydrate series that differ only at the... 

This experiment, first done by Emil Fischer, estabhshed that D-glucose and D-mannose have the same configurations about C3, C4, and C5. Diastereomeric aldoses that differ in configuration at only one carbon (such as D-glucose and D-mannose) are called epimers. In general, any pair of diastereomers that differ in configuration at only a single tetrahedral chirality center can be called epimers. 

Epimers are diastereomers that differ in configuration at only one... 

Enzyme-substrate complex (Section 24.9) The species formed when a substrate (reactant) binds at the active site of an enzyme. Epimers, epimerization (Sections 18.3A and 22.8) Diastereomers that differ in configuration at only a single tetrahedral chirality center. Epimerization is the interconversion of epimers. 

Tables IX and X also reveal some dramatic differences between NMPP and MDPP. These ligands are diastereomers more precisely, they are epimers since they differ only in configuration at C-3. It is quite reasonable that these ligands should behave differently, since diastereomers have different chemical and physical properties, although sometimes only slightly different. However, NMDPP and MDPP generate considerably disparate behavior both in terms of the activity and the chiral influence of the catalysts derived from them. Toward every substrate examined thus far the MDPP catalyst has had a very low activity, much lower activity than the NMDPP catalyst. Also, the MDPP catalyst generally gave much lower asymmetric bias than the NMDPP catalyst, and was the only chiral catalyst to give an archiral product11 (two examples).

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