Novel Cage Indoles from a Malaysian Kopsia

Abstract

The EtOH extract of the leaves of Kopsia teoi yielded the octacyclic alkaloids kopsinitarines A−D (1−4) and mersingines A and B (5 and 6), all possessing a novel cage carbon skeleton. The structures of the alkaloids were established by spectral methods and, in the case of kopsinitarine D (4), confirmed by X-ray analysis.

Leuconoxine, Kopsinitarine, Kopsijasmine, and Kopsinone Derivatives from Kopsia

“…4 In continuation of our studies on the Malaysian members of this genus, [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] we report the structures of four new indole alkaloids, viz., 6-oxoleuconoxine (1) from K. griffithii King & Gamble var. griffithii 3 and kopsinitarine E (2), kopsijasminine (3), and kopsonoline (4) from K. teoi L. Allorge.…”

“…All these features are strongly reminiscent of the cage kopsinitarines, previously obtained from the leaf extract of the same plant. 20,22 Thus, the AX doublets at δ 5.24 and 2.63 are due to H-5 and H-6, respectively, while the other pair of doublets at δ 4.10 and 3.57 are due to H-17 and H-21, respectively, with W-coupling of 2 Hz. The characteristic quaternary resonance at δ 87.6 is due to C-16.…”

Total Synthesis of Kopsinitarine E

“…The remarkable natural products obtained from Kopsia species include kopsine [2] (Figure 1), methyl chanofruticosinates [3] and lundurines [4] . In 1996, Kam and co‐workers reported the isolation of kopsinitarines A–D from the leaves of Kopsia teoi [5] . Eleven years later, kopsinitarine E, a new member of this family, was identified by the same group from another Kopsia resource [6] .…”

“…[4] In 1996, Kam and co-workers reported the isolation of kopsinitarines A-D from the leaves of Kopsia teoi. [5] Eleven years later, kopsinitarine E, a new member of this family, was identified by the same group from another Kopsia resource. [6] Structurally, these five alkaloids have an intriguing octacyclic framework including a central cage unit circumscribed by two five-membered rings and three six-membered rings.…”

Monoterpenoids

“…The absolute configuration of incarvilline 12 from the same source has been determined by X-ray methods, and the structure of hydroxyincarvilline 13 has been elucidated. 13 X-Ray techniques have also been utilised 14 in a determination of the structure of the novel kinabalurine 14, an epimer of incarvilline 12, which has been isolated from Kopsia pauciflora. The new compound kopsilactone 15 has been found 15 in Kopsia macrophylla.…”