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Two older prefixes still commonly used to distinguish diastereomers are threo and erythro. In the case of saccharides, when drawn in the Fischer projection the erythro isomer has two identical substituents on the same side and the threo isomer has them on opposite sides. [ 7 ]
Erythrose is a tetrose saccharide with the chemical formula C 4 H 8 O 4.It has one aldehyde group, and is thus part of the aldose family. The natural isomer is D-erythrose; it is a diastereomer of D-threose.
Several isomers exist with the formula H−(C=O)−(CH 2)−(CHOH) 3 −H, but in deoxyribose all the hydroxyl groups are on the same side in the Fischer projection.The term "2-deoxyribose" may refer to either of two enantiomers: the biologically important d-2-deoxyribose and to the rarely encountered mirror image l-2-deoxyribose.
Threose is a four-carbon monosaccharide with molecular formula C 4 H 8 O 4.It has a terminal aldehyde group, rather than a ketone, in its linear chain and so is considered part of the aldose family of monosaccharides.
Four isomers of methylphenidate are possible, since the molecule has two chiral centers. One pair of threo isomers and one pair of erythro are distinguished, from which primarily d-threo-methylphenidate exhibits the pharmacologically desired effects. [119] [149] The erythro diastereomers are pressor amines, a property not shared with the threo ...
The enzyme erythro-3-hydroxyaspartate ammonia-lyase (EC 4.3.1.20) catalyzes the chemical reaction erythro -3-hydroxy- L -aspartate ⇌ {\displaystyle \rightleftharpoons } oxaloacetate + NH 3 This enzyme belongs to the family of lyases , specifically ammonia lyases, which cleave carbon-nitrogen bonds.
Very often, cis–trans stereoisomers contain double bonds or ring structures. In both cases the rotation of bonds is restricted or prevented. [4] When the substituent groups are oriented in the same direction, the diastereomer is referred to as cis, whereas when the substituents are oriented in opposing directions, the diastereomer is referred to as trans.
Because electron donating groups are both ortho and para directors, separation of these isomers is a common problem in synthetic chemistry. Several methods exist in order to separate these isomers: Column chromatography will often separate these isomers, as the ortho is more polar than the para in general.