Synthesis of very-long-chain bifunctional and isotope-labeled compounds for biochemical investigations into novel compounds in plant cuticular waxes

Plant cuticles are the interface for plant-environment interactions, and the first barrier protecting plants from environmental stresses such as water loss and pathogens. Structurally, the cuticle consists of a hydrophobic polymer lattice, cutin, and cuticular waxes deposited inside and outside cutin. The major components of the cuticular waxes are aliphatics derived from very-long-chain (VLC) fatty acids, such as alkanes and aldehydes. Besides compounds with primary functionalities, some compounds with two or more functional groups have also been identified in cuticular waxes. However, only limited knowledge about them has been acquired so far. The current work was to identify novel 1,2- and 1,3-bifunctional wax compounds from various plant species, in order to expand our current understanding of their structure, biosynthesis and function in plant cuticles. Synthetic methods were first developed to produce various VLC 1,2- and 1,3-bifunctionalized standard compounds for current and future structure elucidation studies. Unknown compounds found in Cosmos bipinnatus petal wax were identified as alkane-1,2-diol monoacetates by GC-MS, with chain lengths ranging from C20 to C24. The ratio between the primary and the secondary monoacetates was quantified to be 3:5, as opposed to the thermodynamic equilibrium ratio of 7:3. Novel β-hydroxy acid methyl esters were also identified from Aloe arborescens leaf wax, with chain lengths ranging from C26 to C30. In addition, two NMR-based methods were established to study the stereoconfigurations of alkane-1,2-diols from C. bipinnatus petal wax, and the carbons bearing secondary hydroxyl functionality were determined to have predominately the R-configuration. Apart from the research on bifunctional compounds, synthetic methods to produce β-deuterium labeled VLC substrates were also established. The resulting C30 fatty acid methyl ester was double-labeled and can be used directly or indirectly as substrates in future biochemical assays. At last, the hypothetic substrate for the CER1 enzyme implicated in wax alkane biosynthesis, C30 aldehyde, was synthesized and used in in vivo assays with heterologously expressed protein.Science, Faculty ofChemistry, Department ofGraduat