Hence, they occur when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other.
Each stereocenter gives rise to two different configurations and thus typically increases the number of stereoisomers by a factor of two.
This difference in stability causes galactose to be absorbed slightly faster than glucose in human body.
Two widely accepted prefixes used to distinguish diastereomers on sp³-hybridised bonds in an open-chain molecule are syn and anti.
Masamune proposed the descriptors which work even if the groups are not attached to adjacent carbon atoms.
[7] When drawn as a zig-zag chain, the erythro isomer has two identical substituents on different sides of the plane (anti).
These prefixes are not recommended for general use because it is often difficult to discern how to apply their definitions to particular comounds.
These meso compounds are molecules that contain stereocenters, but possess an internal plane of symmetry allowing it to be superposed on its mirror image.
Diastereomerism can also occur at a double bond, where the cis vs trans relative positions of substituents give two non-superposable isomers.
In the case of diastereomerism occurring at a double bond, E-Z, or entgegen and zusammen (German), is used in notating nomenclature of alkenes.