Cephalotaxus harringtonia var

An isomeric alkaloid (alkaloid E) was isolated from S. pedunculata and found to be the major alkaloid in S. multiflora R.Br. (55). Values of 4.0 and 11 Hz for J3A suggested that it was the C-3 epimer 81b of schelhammericine. Structure 81b was proved by identification of 3-epischelham-mericine with 2,7-dihydro-3-epischelhammeridine (see Scheme 23) 84). Later on, another group reported the isolation of 81b from P. comosa, and was able to convert 3-epischelhammerine (80b) to 81b by chlorination and reduction, as shown in Scheme 23 (57). Cephalotaxus harringtonia var. harringtonia has also yielded 3-epischelhammericine 91). 

Powell RG, Madrigal RV, Smith CR, Mikolajczak KL. Alkaloids of Cephalotaxus harringtonia var. drupacea. 11-Hydroxycepha-lotaxine and drupacine. J. Org. Chem. 1974 39 676-680. 

Five Homoerythrina alkaloids (3 R = Me, = H), (3 R + R = OCH2O), (3 R - R = Me), (4 R R = H, Me), and (4 R = R = Me) have been shown to co-occur with cephalotaxine (5 R = H) and its ester derivatives in Cephalotaxus harringtonia var. harringtoniaf The structures of the minor Homoerythrina alkaloids were established by spectroscopic studies and comparison with the known alkaloids (3 R = Me, R — H) and (3 R + R = OCHjO) which had been previously isolated from Schelhammera pedunculata and whose structures and absolute chemistry had been established. The co-occurrence of Homoerythrina and Cephalotaxus alkaloids makes it most attractive to propose that both types are derived from a common dienone (Scheme 1). An alternative biogenetic scheme for the formation of cephalotaxine (5 R = H) from an Erythrina precursor has been previously offered as speculation. Deoxyharringtonine (6), a new alkaloid with antileukemic activity of the same order of magnitude as the other known cephalotaxine alkaloids, has been... 

Takano, 1. Yasuda, M. Nishijima, Y. Hitotsuyanagi, K. Takeya, and H. Itokawa, New Oxygenated Cephalotaxus alkaloids from Cephalotaxus harringtonia var. drupaced, J. Nat. Prod., 1996, 59, 1192 - 1195. 

Several new alkaloids have been isolated recently from Cephalotaxus harringtonia var. drupacea, two of which, harringtonine (Va) and iso-harringtonine (Vb), show inhibitory activity against L 1210 and P388 at dose levels of 0-25 to 4 mg/kg and 0-75 to 12 mg/kg respectively [43, 44]. The structure of the heterocyclic portion of these molecules has been established [45] by spectroscopic and x-ray crystallographic studies on cephalotaxine and its methiodide, and the terpenoid portion by spectroscopic analysis of... 

A reductive radical process has also been developed from aryl halides. Scheme 25.35 shows a cascade reductive process (78 79) used in the synthesis of cephalezomine This alkaloid was isolated from the leaves of Cephalotaxus harringtonia var. nana and shows cytotoxic activity against human epidermoid carcinoma KB cells. 

Other alkaloids in the Al(6)-alkene series have been reported. Two isomeric alkaloids (C20H27NO3) were obtained from Cephalotaxus harringtonia K. Koch var. harringtonia. Their spectroscopic properties closely resembled those of schelhammericine except that their NMR spectra revealed the presence of two aromatic methoxyl groups in place of the methylenedioxy group of schelhammericine. The alkaloids were therefore 3-epihomo-2,7-... 

Cephalotaxus harringtonia K. Koch var. fastigiata Rehder (leaves) I-6-Methyl-I-2,3-dihydroginkgetin (36) I-6-methyl-I-2,3-dihydrobilobetin (35) I-6-methyl-I-2,3-dihydrosequoiaflavone (33). Sasaki et al., 2008[224]. 

Oppenauer oxidation gave the hemiketal (16). Furthermore, hydrolysis of the diacetate (14 R = R = Ac) in aqueous dioxan at ambient temperatures resulted in epimerization at C-11. All these reactions are best accommodated by the proposed stereochemical formulation (14 R = R = H) for 11-hydroxy-cephalotaxine. Interestingly, this formulation represents the most hindered of four possible geometric isomers. The alkaloids (14 R = R = H) and (15) are unique to C. harringtonia var. drupacea. It is not yet clear if drupacine (15) is identical with Alkaloid IV obtained by Asada during an extensive reinvestigation of Cephalotaxus species. ... 

Homoharringtonine (18) is an alkaloid of unusual structure and belongs to harringtonine class, which is structurally characterized as cephalotaxine esters. These compounds have been exclusively isolated from Cephalotaxus plants, including C. fortunei Hook F and C. harringtonia K. Koch var. harringtorda [88]. 

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