J Chem Crystallogr (2009) 39:474–477
DOI 10.1007/s10870-008-9507-7
ORIGINAL PAPER
X-ray Crystal Structure of Grandiflorenic Acid [(2)-kaura-9(11)-
16-dien-19-oic Acid] Methyl Ester, a Compound Formerly
Considered as an Oily Derivative
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Perla Cruz-Mondragon Æ M. Concepcion Lozada Æ
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Benjamın Ortiz Æ Raul G. Enrıquez Æ
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Manuel Soriano-Garcıa
Received: 20 October 2007 / Accepted: 13 November 2008 / Published online: 4 December 2008
Ó Springer Science+Business Media, LLC 2008
Abstract Grandiflorenic acid [(-)-kaura-9(11)-16-dien-
19-oic acid] methyl ester (2), C21H30O2, was synthesized
from grandiflorenic acid, isolated from the plant Montanoa
tomentosa. Compound (2) was formerly described as an
oily derivative. X-ray diffraction analysis of (2) demon-
strated that it consists of four rings, three six-membered
rings (I, II and III) and one five-membered ring (IV). I, II
and III rings occur in chair, twist, and envelope confor-
mations, respectively. Ring IV occurs in a conformation
between envelope and half-chair. The crystal of grandif-
lorenic acid methyl ester is in monoclinic crystal system
with space group P21, lattice constants: a = 7.2170(10),
parent grandiflorenic (or kauradienoic) acid 1 and related
compounds [1].
We have previously carried out a comparative study of
the solution and crystal structures of three major terpenic
acids present in Montanoa tomentosa including the parent
acid compound 1 used herein [2].
The synthesis of grandiflorenic acid and its methyl ester
derivative 2 prepared with diazomethane has been reported
[3], and the latter compound was described as an uncrys-
tallizable oil although its spectroscopic data (IR, 1H-NMR,
MS) agree with the expected structure. Since other reports
refer to the isolation of 1 and its derivatization into the
methyl ester 2 [4, 5] a definitive proof of structure is
necessary to meet the growing importance in assessing the
molecular arrangements for this type of compounds [6]. In
the present work, the esterification of grandiflorenic acid
was accomplished with an ethereal solution of diazo-
methane produced by reaction of N-nitroso-methyl urea
and aqueous KOH. The reaction gave a single product by
TLC which proved adequate to obtain single crystals of 2.
In this paper, we report the synthesis and crystal struc-
ture of grandiflorenic acid methyl ester 2 derived from
N-nitroso-methyl urea/KOH/eter system with grandiflore-
nic acid 1.
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b = 11.4170(10), c = 11.2850(10) A, b = 98.700(10)°,
3
V = 919.1(2) A and Z = 2.
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Keywords Diterpenes ꢀ Kauradienoic acid derivative ꢀ
Structure and stereochemistry
Introduction
The synthesis and assessment of the spatial conformation
of grandiflorenic acid methyl ester 2 is a relevant topic due
to the important pharmacological effects reported for the
The need for a definitive proof of the crystal structure of 2
is due to the growing importance in assessing the molecular
arrangements known for this type of compounds [6].
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P. Cruz-Mondragon ꢀ B. Ortiz ꢀ R. G. Enrıquez ꢀ
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M. Soriano-Garcıa (&)
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Instituto de Quımica, Universidad Nacional Autonoma de
Mexico, Circuito Exterior, Ciudad Universitaria, Mexico 04510,
DF, Mexico
e-mail: soriano@servidor.unam.mx
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Experimental
Synthesis
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M. Concepcion Lozada
Departamento de Sistemas Biologicos, UAM-Xochimilco,
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The title compound 2 was synthesized by addition of an
ethereal solution (20 mL) of N-nitroso-N-methyl urea (5 g)
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Calzada del Hueso 1100 Col. Villa Quietud, 04960 Coyoacan,
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Mexico DF, Mexico
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