[Thesis]. Manchester, UK: The University of Manchester; 2020.
Phosphatidylinositols (PI) such as phosphatidylinositol-3,4,5-triphosphate (PIP3)
play a vital role in cell signalling through recruiting proteins to the plasma membranes.
PIP3 is the natural substrate of phosphatase and tensin homologue deleted from chromosome
10 (PTEN), a tumour suppressor protein which has been discovered to be one of the
most frequently mutated proteins in cancers. PIP3 is dephosphorylated to phosphatidylinositol-4,5-biphosphate
(PIP2) by PTEN, leading to a decrease in the membrane localisation of AKT, a cell
survival kinase. In PTEN-null or mutated cells, this dephosphorylation cannot occur
thus leading to an accumulation in the levels of PIP3 at the plasma membrane, resulting
in increased activity of AKT and thereby increased cell proliferation and growth.
Previous research into small molecule inhibitors showed that the binding of PIP3 can
be affected by disrupting the interaction between PIP3 and the PH domain of AKT. The
purpose of this project was to prepare analogues of phosphatidylinositol (PI) with
varying lipophilic chain lengths in the phosphonate group at the 1-position, in order
to establish their effects in cells. Initial synthesis led to the formation of 1,4
myo-inositol diol through the selective protection of the hydroxyl groups. Following
on from this, phosphorus chemistry was explored in the hope of identifying a suitable
phosphorus fragment, for the selective phosphorylation of the 1-position of the protected
myo-inositol headgroup. Hydrolysis and oxidation issues with phosphorus(III) species
highlighted issues with this line of chemistry, so attentions turned to phosphorus(V)
chemistry. It was revealed that the selective protection of the 1,4-diol was not possible,
with phosphorylation reactions leading to the bis-phosphorylated product. This led
to the design and synthesis of a penta-protected myo-inositol headgroup which was
phosphorylated with a newly synthesised phosphorylating agent with the POM prodrug
This project also sought to form a PI analogue in which the myo-inositol headgroup
is modified, with the 2 and 6 hydroxyl groups removed. The desired stereochemistry
of the 1,3,4 and 5 hydroxyl groups were set through a sequence of steps leading to
the successful formation of the headgroup which was phosphorylated to yield the desired
phosphonate. This synthetic approach was used to synthesis four analogues with varying
alkyl chain lengths and three of these phosphonates were evaluated using MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide) and sulforhodamine B (SRB) assays. From these studies, an apparent SAR was
established with the longer chain phosphonates displaying higher activity.