Syntheses Of Nitrogen-containing Heterocyclic Compounds

Alkaloids are a very important class of natural compounds with high biologicalactivity and the medicinal value. Polyhydroxylated5S-methylpiperidines are potentialinhibitors of glycosidases and glycoprotein-processing enzymes. Now they havebeing widely investigated as drug candidates to treat a variety ofcarbohydrate-mediated diseases such as diabetes and cancer metastasis. Plantscontaining pyrrolidine alkaloids are also used as herbal and medicinal tea. Forexample, Japanese residents often drink daisy tea, which is rich in pyrrolidinealkaloids. Alkaloids possessing the pyrroloindoline framework exhibit a broad arrayof biological properties, ranging from antibacterial and anticancer activities to theinhibition of cholinesterase.There are few natural products containing pyrazole, pyrazoline or pyrazolidinemoiety. Examples include newbouldine, withasomnine, and four other derivatives.This may be because that the evolution of organisms has produced few enzymeswhich can cuase formation of an N-N bond. Pyrazole, pyrazoline, and pyrazolidinering systems are important heterocycles, not only in medicinal chemistry because oftheir antibacterial, antipyretic, antidepressant and anti-inflammatory activity, but alsoin material chemistry for their role in nanocrystal investigation or as brighteningagents.In the thesis,4R,5S-dihydroxy-2S-hydroxymethylpiperidine and4S,5R-dihydroxy-2S-hydroxymethylpiperidine were obtained following a sequences ofreactions including Stevens rearrangement, RCM reaction and dihydroxylation.Besides, asymmetric synthesis of pyrazolidines was realized through Stevensrearrangement and5-exo-trig cyclization.