Preferred Label : α (alpha), β (beta);
IUPAC definition : absolute stereodescriptors originally devised for steroid nomenclature. however in
this sense it is only meaningful if there is an agreed absolute configuration and
orientation of the structure so as to define the plane and which way up the molecule
is represented. substituents above the plane of the steroid are described as ß and
are shown as a solid line ( or ); those below the plane are described as a and are
shown by a broken line ( or ). the extension of this system to tetrapyrroles has
been documented and it has been widely used elsewhere.; relative stereodescriptors used by chemical abstracts service to describe the configuration
of a cyclic molecule (including suitable polycyclic systems) with several stereogenic
centres whereby the a side of the reference plane is the side on which the substituent
with cip priority lies at the lowest numbered stereogenic centre. the other side is
ß.; relative stereodescriptors used in carbohydrate nomenclature to describe the configuration
at the anomeric carbon by relating it to the anomeric reference atom. for simple cases
the anomeric reference atom is the same as the configurational reference atom. thus
in a-d-glucopyranose the reference atom is c-5 and the oh at c-1 is on the same side
as the oh at c-5 in the fischer projection.;
Origin ID : A00003;
See also
- See also (suggested by CISMeF)
absolute stereodescriptors originally devised for steroid nomenclature. however in
this sense it is only meaningful if there is an agreed absolute configuration and
orientation of the structure so as to define the plane and which way up the molecule
is represented. substituents above the plane of the steroid are described as ß and
are shown as a solid line ( or ); those below the plane are described as a and are
shown by a broken line ( or ). the extension of this system to tetrapyrroles has
been documented and it has been widely used elsewhere.
relative stereodescriptors used by chemical abstracts service to describe the configuration
of a cyclic molecule (including suitable polycyclic systems) with several stereogenic
centres whereby the a side of the reference plane is the side on which the substituent
with cip priority lies at the lowest numbered stereogenic centre. the other side is
ß.
relative stereodescriptors used in carbohydrate nomenclature to describe the configuration
at the anomeric carbon by relating it to the anomeric reference atom. for simple cases
the anomeric reference atom is the same as the configurational reference atom. thus
in a-d-glucopyranose the reference atom is c-5 and the oh at c-1 is on the same side
as the oh at c-5 in the fischer projection.
