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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.
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 ]
The natural isomer is D-erythrose; it is a diastereomer of D-threose. [3] Fischer projections depicting the two enantiomers of erythrose. Erythrose was first isolated in 1849 from rhubarb by the French pharmacist Louis Feux Joseph Garot (1798-1869), [4] and was named as such because of its red hue in the presence of alkali metals ...
Ribulose is a ketopentose — a monosaccharide containing five carbon atoms, and including a ketone functional group.It has chemical formula C 5 H 10 O 5.Two enantiomers are possible, d-ribulose (d-erythro-pentulose) and l-ribulose (l-erythro-pentulose).
[159] [162] [163] [164] The erythro isomer was eliminated, and now modern formulations of methyphenidate contain only the threo isomer in a 50:50 mixture of d- and l-isomers. [159] Methylphenidate was first used to allay barbiturate-induced coma, narcolepsy and depression. [165] It was later used to treat memory deficits in the elderly. [166]
The second reaction is the organic reduction of 1,2-diphenyl-1-propanone 2 with lithium aluminium hydride, which results in the same reaction product as above but now with preference for the erythro isomer (2a). Now a hydride anion (H −) is the nucleophile attacking from the least hindered side (imagine hydrogen entering from the paper plane).
Its strange that this decription of the definition of a diastereomer does not mention E/Z alkene isomers!--175.38.163.188 18:26, 15 August 2013 (UTC) Cis–trans isomerism does not involve chirality. So the E and Z forms are isomers, but not enantiomers, and as such can't be diastereomers either.
Epimerization is a chemical process where an epimer is converted to its diastereomeric counterpart. [1] It can happen in condensed tannins depolymerization reactions. Epimerization can be spontaneous (generally a slow process), or catalysed by enzymes, e.g. the epimerization between the sugars N -acetylglucosamine and N -acetylmannosamine ...