Cedronin and 7-epi-Cedronin: X-ray Crystal Structure Analysis

Abstract

hTrlACT.--The structure and stereochemistry of the quassinoid cedronin 111 and the previously unreported 7-epi-cedronin 121 isolated from Simaba redron have been established by X-ray crystal structure analysis. The change in configuration at C-7 produces a minimal change in molecular conformation and crystal packing. Cedronin [7-epi-cedronin] crystallizes in the monoclinic space group P2, with cell parameters a=6.794(2) [6.779(1)1, b= 18.684$2) [19.029(3)], r=7.573(2) [7.419(2)]& p= 116.67(2)" [115.56(1)7, U=859 [863]A3, D,= 1.405 11.3981 g cm-3 for Z=2, Mo K& radiation (h=0.71069A); final R factor=0.038 [0.031] for 1766 [l819] observed data with I>30(1).Quassinoids, bitter principles of simaroubaceous plants, continue to excite interest because of the complexity and diversity of their structures and because they exhibit a wide range of biological properties including, in some cases, antileukemic activity (1). The CI9 quassinoid cedronin was isolated from the seeds of Brazilian Simaba cedron Planch. (Simaroubaceae) by J. Polonsky ( 2 ) , who identified it as 7-dihydrosamaderin B( 3 ) and later assigned it the 7a-hydroxy configuration ( 4 , 5 ) , but few details of the characterization are available in the primary literature. In our investigation of the seeds and leaves of Guyanese S. cedron, we isolated small quantities of two quassinoids. The first, mp 238-240", was more abundant in the seeds, and appeared to be Polonsky's cedronin' 111. The second, mp 232-234", was more abundant in the leaves, and its spectroscopic characteristics indicated that it was a new stereoisomer of cedronin, almost certainly the C-7 epimer with an equatorial OH group. X-ray crystal structure analysis offered the best method for establishing unequivocally the structure and stereochemistry of each of these compounds, and for making a detailed comparison of the stereochemistry of these two complex, multiply-bridged, polycyclic compounds. DISCUSSIONCrystal data and the final atomic positional parameters in the two structures are given in Tables 1 and 2, respectively. * The X-ray analysis establishes the two isomers as 1 X = O H , Y = H cedronin 2 X=H, Y=OH 7-epi-cedronin 'An authentic sample of the original cedronin is no longer available.'Atomic coordinates for these structures have been deposited with the Cambridge Crystallographic Data Centre and can be obtained on request from Dr.

Comparative X‐Ray and Conformational Analysis of a New Crystal of 13α,21-Dihydroeurycomanone with Eurycomanone fromEurycoma longifoliaand Their Anti-Estrogenic Activity Using the Uterotrophic Assay

“…The calculated results demonstrated that ring A adopted the conformation closer to the flattened chair rather than to the half-boat in which the approximate plane of symmetry passed through C(3) and C (10). The distorted half-boat of ring A was also supported by the torsion angles of Φ 1,2,3,4 = 3.2°and Φ 2,3,4,5 = −1.0° [27]. Furthermore, molecular modeling calculations were performed on 1 using the MM2 force field from Chem3D Ultra 9.0 (Cambridge-Soft) in order to determine the ring conformations.…”

“…In a similar manner, the flatten- 17, 111.77° (19), 110.20° (17) and 118.94° 17, respectively. Maximum torsion angle of 73.3°(Φ 8,9,11,12 ) supported the distorted chair of ring C [27]. Furthermore, the corresponding endocyclic torsion angle measurements (ΔC s 9,13 = |Φ 8,9 + Φ 9,11 | + |Φ 8,14 + Φ 11,12 | + |Φ 13,14 + Φ 12,13 | = 12°) [26] suggested that the approximate plane of symmetry of the flattened chair form of C passed through C(9) and C (13).…”

Triterpenoids

“…'~~ The structure of 7-epicedronin (198), which occurs with cedronin (199) in S. cedron, has been established by X-ray analysis. 186 The neoquassin derivative (200) has been isolated from Quassia amara.18' Quassin and several of its congeners in the root bark of Picrasma quassioides show acute insecticidal activity against the American cockroach.la8 During this study a new compound, 14P-hydroxypicrasin (20 l), was isolated.188 Attempts to oxidize quassin with Jones' or Collins' reagents afforded the unexpected product (202) whose structure was established by X-ray analysis.1aa The details of the crystal structure analysis of bruceine B have appeared. lgo The antimalarial activity of some quassinoids is dependent on the nature of the ester group attached to C-15.1g1 Methods for converting inactive quassinoids into cytotoxic compounds by introduction of acyl or alkyl substituents at C-15 have been described.lg2…”