Synthesis, DNA-PK inhibition, anti-platelet activity studies of 2-(N-substituted-3-aminopyridine)-substituted-1,3-benzoxazines and DNA-PK and PI3K inhibition, homology modelling studies of 2-morpholino-(7,8-di and 8-substituted)-1,3-benzoxazines

Abstract A number of new 2-(pyridin-3-ylamino)-4 H -(substituted) benz[ e ]-1,3-oxazin-4-ones were synthesized 10a – g . These were then reacted with the hydro-halogen salt of 2, 3 and 4-(halo-methyl) pyridine in the presence of Cs 2 CO 3 to give eighteen new 2-( N -substituted (pyridin-3-ylmethyl) amino)-substituted-1,3-benzoxazines (compounds 11a – i , 13a – c , and 15a – f ). X-ray crystallography was used to confirm that the 2- N -substituted structures 11 and 13 were formed rather than the 3- N -substitution analogues 12 and 14 . Eleven of the new compounds were tested for their effect on collagen induced platelet aggregation and it was found that the most active inhibitory compound was 8-methyl-2-(pyridin-3-yl(pyridin-3-ylmethyl)amino)-7-(pyridin-3-ylmethoxy)-4 H -benz[ e ]-1,3-oxazin-4-one 15e with an IC 50 of 10 ± 2 μM. DNA-dependent protein kinase (DNA-PK) inhibition data for 12 previously prepared 2-morpholino substituted-1,3-benzoxazines (compounds 19 – 31 ) were measured and showed high to moderate activity where the most active compound was compound 27 with an IC 50 of 0.28 μM. Furthermore DNA-PK inhibition data for six newly prepared 2-( N -substituted (pyridin-3-ylmethyl) amino)-substituted-1,3-benzoxazines (compounds 11b , 13a – b , 15a – b and 15e ) and 8-methyl-7-(pyridin-3-ylmethoxy)-3-(pyridin-3-ylmethyl)-2 H -benz[ e ]-1,3-oxazin-2,4(3 H )-dione 17d were measured and moderate to low inhibitory activity was observed, with the most active of the compounds in this series being 8-methyl-2-(pyridin-3-yl(pyridin-3-ylmethyl)amino)-7-(pyridin-3-ylmethoxy)-4 H -benz[ e ]-1,3-oxazin-4-one 15e with an IC 50 of 2.5 μM. PI3K inhibition studies revealed that compound 27 is highly potent (IC 50 for PI3Kα = 0.13 μM, PI3Kβ = 0.14 μM, PI3Kγ = 0.72 μM, PI3Kδ = 2.02 μM). Compound 22 with 7-[2-(4-methylpiperazin-1-yl)ethoxy] group shows greater inhibition of DNA-PK over PI3K. Docking of some 2-morpholino-substituted-1,3-benzoxazine compounds 19 – 31 within the binding pocket and structure–activity relationship s (SAR) analyses were performed with results agreeing well with observed activities.