|其他摘要||This thesis elaborated the studies on the alkaloids of daphniphyllum plants, Daphniphyllum calycillum Benth (collected in Xishuangbanna of Yunnan province and Dinghu Mountain in Guangdong province, respectively), Daphniphyllum longeracemosum Rosenth, and Daphniphyllum yunnanense C. C. Huang, and on chemical constitutes of Cipadessa cinerascens. By a variety of chromatography over various materials, 65 compounds, including 28 new ones, were isolated, which mainly covered daphniphyllum alkaloids with various skeleton and tetranortriterpenoids. Their structures were mainly elucidated on the basis of spectroscopic studies.
Chapter 1 Studies on alkaloids of Daphniphyllum calycillum Benth (collected in Xishuangbanna of Yunnan province)
Thirteen Daphniphyllum alkaloids, including five new ones, were isolated and elucidated from rough alkaloids part of leaves and twigs of Daphniphyllum calycillum Benth. Among them, compound 1 was a novel one with rearranged skeleton. Broading signals, which were observed in 1D-NMR spectra, suggested that several interconverted conformational isomers of 1 might equilibrate in solution. By spectral, crystallographic, chemical, thermodynamic, and computational means, we elucidated structures of its three interconverting conformers.
Chapter 2 Studies on alkaloids of Daphniphyllum calycillum Benth (collected in Dinghu mountain in Guangdong province)
Eight Daphniphyllum alkaloids, including a new one (calycilactone A), were isolated and elucidated from rough alkaloids from leaves of Daphniphyllum calycillum Benth. Calycilactone A (1) is a new hexacyclic daphniphyllum one with novel skeleton. Biogenetically, compound 1 originated from daphnilactone B by pinacol rearrangement.
Chapter 3 Studies on alkaloids of Daphniphyllum longeracemosum Rosenth
Investigation of alkaloid constituents of Daphniphyllum longeracemosum Rosenth has resulted in the isolation of fifteen compounds. And six were new ones. Among them, longeracinphyllin B was a novel daphniphyllum alkaloid with seco-10,17-longeracinphyllin A skeleton; and longeracinesides A–D (25–28) were the other type of alkaloids. Compounds 25–28 may be visualized as cycloadducts of corresponding Daphniphyllum C-21 alkaloids and deacetylasperuloside via intermolecular Diels-Alder reaction. Stereoselectivity of cycloaddition was studied by computational methods, and it was suggested that no enzyme were involved in the high stereo-selectivity reaction.
Chapter 4 Studies on alkaloids of Daphniphyllum yunnanense C. C. Huang
In this work, fifteen alkaloids, including ten new ones, were isolated from leaves and twigs of Daphniphyllum yunnanense C. C. Huang. Among them, Yunnandaphninines C and D were the key intermediates, connecting two types of alkaloids: yuzurimine and calyciphylline A.
Chapter 5 Studies on tetranortriterpenoids of Cipadessa Cinerascens (Pell.) Hand.-Mazz
Seven tetranortriterpenoids and eight the other types of natural products, isolated from leaves of Cipadessa cinerascens (Pell.) Hand.-Mazz, were reported in this chapter. Six new tetranortriterpenoids were isolated, which might be originated from a cipadesin-A-type tetranortriterpenoid via pinacol rearrangement.
Chapter 6 Review
Advances research of Diels-Alder reaction in the biosynthesis of natural products was reviewed.|