Homoerythrina alkaloid isolation

Five new homoerythrina alkaloids have been isolated from this plant in addition to others which were known. Their properties and... 

The C-Homoerythrina alkaloids are a relatively recently identified group, the first examples being isolated and identified from Schelhammera pedunculata F. Muell. in 1968 (81). Homoerythrina alkaloids have been isolated from all three species of Schelhammera (Liliaceae), in which they constitute a further addition to the various biosynthetically related alkaloids within the family Liliacea (82-85)-, from the leaves of species of Phelline (Ilicacea), where their presence raises some doubts about the taxonomic classification of the genus (86-88)-, and from the roots and stems of species... 

Many members of the Homoerythrina group occur with their C-3 epimers, in contrast to the Erythrina group, and despite the fact that they appear in relatively few plant species, over 20 individual Homoerythrina alkaloids have been isolated, although the structures of two of them remain incomplete because of insufficient amounts of samples. Those alkaloids of known struc-... 

The alkaloids were best isolated from the ethanol extract of the plant material, partially fractionated by counter-current distribution, and subsequently purified by preparative chromatography. Of the 11 known Cephalotaxus alkaloids (105-115 in Figs. 8 and 9), cephalotaxine (105a) is ubiquitous and the most abundant (up to 64% of the total alkaloid extract) in all species examined. C. wilsoniana Hay., which yields only minor quantities of cephalotaxine, is the exception, however it is rich in Homoerythrina alkaloids,... 

The first two homoerythrina alkaloids to be isolated (82) were schelham-merine (80a) and schelhammeridine (77a), and since various species of... 

Arguing from structural similarities, it was originally suggested (10) that the Cephalotaxus alkaloids could be derived in vivo from the same precursor as the aromatic erythrina bases, but since Cephalotaxus and homoerythrina alkaloids have been isolated (90) from E. wilsoniana, it has been postulated (10b, 89) that both groups have a 1-phenethyltetrahydroisoquinoline as a common precursor (Scheme 36). Tyrosine is incorporated (122) into cepha-lotaxine, but the labeling pattern did not seem to be consistent with a... 

New homoerythrina alkaloids, alkaloid II (246), III (247), and VI (248), were more recently isolated from Cephalotaxus harringtonia (71). 

The known Homoerythrina alkaloids B (3 R = Me, R = H) and E (3 R + R = OCHjO) have been isolated from Schelhammera undulata. These have been previously obtained from S. pedunculata and S. multiflora. 

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... 

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