Carbohydrate Chemistry Flashcards
what is the general formula of a carbohydrate
Cx(H20)y
what are carbohydrates
polyhydroxy aldehydes or ketones or substances that can be hydrolysed to give polyhydroxy aldehydes or ketones
What increases as number of carbons increases
isomers of carboyhdrate
what is important if we need to develop specific oligosaccharides to examine its biological properties
important to develop synthetic methods which only allow access to the regio and stereoisomer of choice
what are monosaccharides
are defined as monomer units that are not connected to other such units
what are disaccharides
formed when two monosaccharides join together
what are trisaccharides
when three monosaccharides units join together
what is a polysaccharide
structures which contain more than ten monosaccharides joined together by glycosidic bonds
what are carbohydrate units joined together by
glycosidic bonds
what are the two positions a group can lie
equatorial or axial
what are the two faces of chair conformation
alpha (bottom)
beta (beta)
Role of Carbohydrates
energy storage
structural compoenents of skeletal components
first point of contact when cells interact
cell recognition and differentiation
why are carbohydrates the first point of contact when cells interact
carbohydrates reside on the surface of all cells and are involved in a multitude of biological processess
what do cancer cells do
they differ from healthy cells and often temrinate in sialic acid which has a carboxylic acid functional group
give 3 examples of tumour associated carbohydrate antigens
Sialyl lewis
T-Antigen
MBr 1 antigen
What therapeutic opportunities exist for carbohydrates
vaccination approaches based on antibodies to disease associated carbohydrates
inhibition of the enzymes associated with the synthesis of disease associated carbohydrates
blocking the interactions of the disease asociated carbohydrates with their receptors
developing prodrugs based on disease associated enzymes
inhibition of that enzyme is a plausible is a reasonable decision
If a glycosidase or glycosyl transferase enzyme is up-regulated and causes unusual carbohydrates to form
when is inhibition of that enzyme used
cancer
aids
diabetes
what is a prodrug
a biologically inactive compound which can be metabolized in the body to produce a drug.
Theoretically what does oligosaccharides need to be produced
one hydroxyl group of a monosaccharide acceptor with the anomeric center of a further monosaccharide donor to furnish a disaccharide unit.
a further monosaccharide donor to furnish a disaccharide unit.
Give example of chemical problems which complicate the process
reactivities of hydroxyl groups - all secondary have similar reactivity so hard to bias which reacts first.
possibility of forming different isomers - due to reactions of different hydroxyl groups
the carbohydrate monomers can exist in a variety of forms and the various forms can interconvert upon exposure to aqueous media
what is more thermodynamically stable due to the anomeric effect
alpha anomer
what is anomeric effect
thermodynamic preference for polar groups bonded
to C-1 (the anomeric carbon of a glycopyranosyl derivative) to take up an axial position
what are carbohydrates made in
biological systems using enzymes
what are the advantages of enzymatic synthesis
protecting group strategies are not needed
the reactions occur in aqueous solutions therefor environmentally friendly
allow access to specific regio and stereoisomers
purification is therefore simpler
what are the disadvantages of enzymatic synthesis
expensive
enzymes for access to specific linkages have not yet been isolated cloned and made commercially available
small quantities of materials available
enzymes allow access to specific regio and stereoisomers from natural substrates therefore the preparation of wide liberties of compounds for high throughput analysis is not always viable
what are reactions of carbohydrates dependent on
functional groups within the molecule as it provides the characteristics
what two main properties do reactions of carbohydrates display
polyhydroxy compounds and carbonyl
what are the main charactistics of the hydroxyls
deprotection
protection
what is a protecting group
A temporary alteration in the nature of a functional group so that it is rendered inert under the conditions in which reaction occurs somewhere else in the molecule.
