In this study it is aimed to synthesize potential novel MDM2 inhibitor which has 1,4-oxazepan-5-one skeleton. For this purpose (R)-(4-chlorophenyl)glycine was used as a starting material. Reduction of that with LiAlH4 and the protection of amine by Trt group was performed. After oxidation to aldehyde, direct or stepwise installation of glutaconic to the structure by either Michael type addition or coupling with amine by using HATU was quite problematic and all attempts were failed toward the preparation of this skeleton. Besides, synthesis of 1,4-oxazepan-5-one was also tried starting from chiral aminoalcohol and protected 5-hydroxy-2-pentanoic acid in two steps, first coupling then oxa-Michael addition. However this did not work well too. It seems that presence of activated methylene group might be the main problem in the addition of glutaconic acid reactions. In the second part of this thesis it was aimed to synthesize the 1,2,3-triazole substituted coumarin in order to investigate the potential antiproliferative properties of these over cancer cells. Acetylsalicilic acid was used as starting material in these syntheses. That was transformed 4-acetylene substituted coumarin derivatives as key intermediates then their transformations to corresponding final products was performed by click chemistry.