Acyl phosphonates are interesting precursors for the synthesis of biologically active compounds. In the first part, the acyl phosphonates are synthesized starting from the corresponding acyl chloride. The acyl chlorides are converted into acyl phosphonates by using trialkylphosphites. The reaction of acyl phosphonates with aldehydes in the presence of proline furnished not the suggested aldol products via proline catalyzed aldol reaction but bicyclic products via one pot tricomponent 1,3-dipolar cycloaddition reaction. The formation of the bicyclic compound was suggested as followed / The formation of iminium salt of proline with aldehyde followed by decarboxylation furnished azomethine. The 1,3-dipolar cycloaddition of the formed azomethine with carbonyl group of acyl phosphonate afforded substituted hexahydro pyrrolo oxazole structures. 1,3-Dipolar cycloaddition forms the basis of the most preparatively useful procedures for the synthesis of five-membered heterocycles. One example is the 1,3-dipolar cycloaddition of azomethine ylides (from imines) and alkenes, which allows the stereoselective synthesis of pyrrolidines or proline derivatives.

Chiral pyridines as organocatalysts have been used in asymmetric organic synthesis in recent years. The asymmetric synthesis of camphor fused pyridine type novel organocatalysts were perfomed starting from cheap and easily available natural (+)-camphor. Using camphor fused pyridine skeleton, six organocatalysts 29, 32, 33, 38, 40, and 41were successfully synthesized. The first four nucleophilic and Lewis base catalysts 29, 32, and 33 are different P-oxides and P,N-dioxides which were tested in allylation of aldehydes via allyltrichlorosilane. L-proline amide 38 and D-proline amide 40 can be named as secondary amine catalyst. They were tested in direct aldol reaction between acetone and aromatic aldehydes in aqueous medium. Final group of catalyst is hydrogen bonding type catalyst which is thiourea based 41.

Near-IR dyes that absorb and emit in the red visible or near-IR region have attracted great interest in the fields of medicinal chemistry and biochemistry for the last few decades. This interest is due to the multiple notes of metal ions in biological and enviromental processes. Therefore the development of cation selective and sensitive sensors have been a hot subject for many researchers. Consequently, fluorescence based sensors are the most efficient and favorable ones among its counterparts in the field of sensor research. In this study, we have targeted to synthesize BODIPY based near-IR dyes as a selective fluorophore for Zn (II) and Hg (II) cations. We have also demonstrated that the versatile BODIPY fluorophore can be functionalized for long wavelength emission on the 3 and 5 position of the BODIPY core with multiple and distinct functional groups in a stepwise manner. Thus we are able to link two BODIPY cores with a different absorption wavelengths to each other first time with click chemistry strategy to generate a chemosensor for Hg (II) cation.

The production of enantiopure compounds can be achieved by using dehydrogenases as biocatalysts catalyzing reduction reactions of prochiral compounds such as ketones, aldehydes and nitriles. These dehydrogenases are cofactor dependent enzyme where cofactor is Nicotinamide dinucleotite having some restrictions that limits usage of dehydrogenases in organic synthesis including instability of cofactor in water and high cost. Therefore suitable regeneration method is needed and developed which are enzymatic and electrochemical. We will use an electrochemical approach for the regeneration of reduced co-factors which has been shown in principal with mediators like pentamethylcyclopentadienyl rhodium bipyridine complexes or ferrocenes. This project is European Union project, whose name is Development of Electrochemical Reactors Using Dehydrogenases for Enantiopure Synthon Preparations. All active compounds / mediator, cofactor and enzyme, will be immobilized on the electrode surface of the constructed reactor surface. Therefore only educts and v products will exist in the reactor medium. A gas diffusion electrode will be employed as a counter electrode / which delivers clear protons to the system. Mediator will carry electrons to the cofactor for cofactor regeneration. Then enzyme will use the cofactor and convert substrates to the product in high stereoselectivity. Our part in this project is the synthesis of mediator and suitable linkers for enzyme, cofactor and mediator immobilization. In the first part of the study, Linkers which contain thiol group and disulfide linkage were synthesized because working electrode made of by gold nano particles and immobilization carried out by the help of these groups on gold nano surface. In the second part of the study, mediators were synthesized which are pentamethylcyclopentadienyl rhodium bipyridine complexes and ferrocene derivatives. Synthesized mediators were reacted with linkers by using Click Chemistry and by imine formation in order to convert mediator to the thiol functionalized form.

The thesis subject is mainly involved in Green Chemistry approach. Thiophene, furan and pyridine carboxaldehydes were chosen as starting compounds and vinylation and allylation with Grignard reaction afforded the corresponding racemic heteroaryl substituted allylic and homoallylic alcohols. Subsequent resolution with enzymes (PS-Amano II, Lipozym and Novazym 435) gave enantiomerically enriched alcohols with the e.e. values varied between 65 and 99%. The absolute configurations of all substrates are known. As a result of O-allylation with the common procedure formed the feasible carbon backbone for the ring closing metathesis reaction. All ring closing metathesis reactions were performed by Grubbs&rsquo / catalyst with just 5% catalyst loading. The absolute configurations of dihydrofuran and dihydropyran derivatives are known, since the chiral center configurations of all substrates are preserved throughout all the applied processes.

Numerical descriptors, beginning with Wiener, and then named topological indices by Hosoya, have gained gradually increasing importance along with other descriptors for use in QSAR and QSPR studies. Being able to estimate the physical or chemical properties of a yet nonexistent substance as close as possible is very important due to huge consumption of time and money upon direct synthesis. In addition, one may face safety problem as in the case of explosives. There have been almost hundred topological indices so far in the chemical graph theory literature. However, there is no topological index which is generalizable to all kinds of molecules. In the present study, a novel topological index (TG Index) has been developed and applied to a wide range of organic molecules including explosives for modeling their physical, structural and molecular orbital properties. The index yielded quite successful correlation data with most of the properties considered in this study.

Optically active polychlorinated norbornene systems are important starting compounds for the synthesis of many complex molecules. The synthetic strategy of this study mainly depends upon the enzymatic resolution of hydroxymethyl-substituted polychlorinated norbornene structures. The enantiomerically enriched acetoxymethyl derivatives were synthesized in high ee values by several lipases. The absolute configuration of tetrachlorinated norbornene system was determined by X-ray analysis. The second part of the thesis involves the ruthenium and cerium-catalyzed oxidation reactions of various polychlorinated norbornene derivatives to afford &amp / #945 / -diketones. The regioselectivity of ruthenium catalyst was tested in polychlorinated norbornadiene systems. In the third part of the study, cyclopentanoid derivatives were synthesized in high chemical yield starting from enantio-enriched both tetra- and hexa-chlorinated norbornene derivatives. In the last part of the study, stereo- and regioselective synthesis of carbasugar systems which are potential glycosidase inhibitors were performed. Starting from enantio-enriched acetoxymethyl substituted tetrachloro norbornene system both carbasugar by cleavage of C1-C7 bond and &lsquo / confused&rsquo / carbasugar by cleavage of C4-C7 bond were synthesized.

Cyclitols have attracted a great deal of attention in recent years because of diverse biological activities exhibited by them and also synthetic usefulness in the synthesis of other natural compounds or pharmaceuticals. The presence of hydroxymethyl groups in many cyclitols units building natural products is also attracting a remarkable attention. In this study, novel synthetic strategies leading to cyclitol derivatives including hydroxymethyl groups were investigated and the syntheses of bis-homoinositol derivative 127 and hydroxymethyl containing conduritol derivative 137 were achieved successfully. For the synthesis of bishomo-chiro-inositol (127), lactone derivative 132 was synthesized as key compound. The molecule was functionalized with the use of photooxygenation and epoxidation reactions to get target stereochemistry. For the synthesis of hydroxymethyl containing conduritol 137, hydroxymethyl substituted p-benzoquinone derivative 136 was synthesized as a key compound. Bromination of related double bond, reduction of carbonyl groups and the following substitution of bromine atoms form the basis of our strategy. As a result we enabled to synthesize novel cyclitol derivatives stereoselectively by using commercially available starting compounds and well known reactions.

The racemic homoallylic and homopropargylic alcohol derivatives were resolved by applying chemoenzymatic method using various lipase type enzymes i.e., PS-C II, Lipozyme, CAL-B. The enantiomeric excess values of the resultant alcohols were determined by HPLC. These enantiomerically enriched homoallylic and homopropargylic alcohols were subjected to N-propargylation and N-allylation, respectively, by SN2 and modified Mitsunobu reactions. During the course of all reactions, stereochemistry of the chiral centers were under controlling according to the known reaction mechanisms. The resultant chiral N-tosylated enyne derivatives afforded the corresponding chiral fused cyclopenta[c]pyridinone derivatives (69, 73, 75 and 77) with acceptable chemical yields and excellent diastereoslectivity depending upon the conformational effect on the complete remote stereochemical control for the newly generated chiral centers. The chemoenzymatic applications done with biocatalysis (lipases) and the Pauson-Khand reaction are involved in &ldquo / Green Chemistry&rdquo / approach.

The one electron oxidant Mn(OAc)3 has been used for years for the oxidative addition of 1,3-dicarbonyls to alkenes to give dihydrofuranes. Since cycloheptatriene is in equilibrium with its valance isomer norcaradiene, it will be interesting to study the reaction of CHT derivatives with Mn(OAc)3 in the presence of 1,3-dicarbonyls. In our research, we have observed that unsubstituted cycloheptatriene gave CHT based products. However, when electron withdrawing -CN group was attached to C-7 position of CHT we obtained norcaradiene based products. We have also observed that there exist an equilibrium between [3+2] addition products through 1,5-hydride shift. In addition, we obtained dihydrofurane derivatives in the presence of Mn(OAc)3 from compounds which have already formed C-C bond between 1,3- dicarbonyl and alkene. Formation of dihydrofurane derivatives from these compounds brought up two questions / whether cyclization is going over oxygen atom or not and whether reaction involves a cyclopropane intermediate or not. Despite all efforts, we could not manage to synthesize the required material for the investigation of these questions.