Alkylation Products of a Calix[8]arene Trianion. Effect of Charge Redistribution in Intermediates

Article abstract of DOI:10.1021/jo970029u

The behavior of a well-defined calix[8]arene trianion under alkylation conditions was investigated by reacting the tetraethylammonium salt of p-tert-butylcalix[8]arene trianion with p-methylbenzyl bromide. Chromatography of the reaction mixture afforded the following derivatives in order of decreasing yields: 1,3,5,7-tetrakis-, 1,3-bis-, 1,3,5-tris-, 1,2,4-tris-, and mono(p-methylbenzyl)-p-tert-butylcalix[8]arene, besides trace amounts of 1,4- and 1,5-disubstituted compounds. Comparable results were obtained using p-tert-butylbenzyl bromide. The observed regioselectivity has been explained by assuming that after each alkylation step the left negative charge is redistributed, by exchange equilibria, over the remaining phenolic groups with preferential localization at those positions where contiguous H-bond stabilization is possible and the electrostatic repulsion is minimized. The occurrence of protonation/deprotonation equilibria allows the formation of 1,3,5,7-tetrasubstituted calix[8]arene.

Full text of DOI:10.1021/jo970029u

4236
J . Org. Chem. 1997, 62, 4236-4239
Alk yla tion P r od u cts of a Ca lix[8]a r en e Tr ia n ion . Effect of Ch a r ge
Red istr ibu tion in In ter m ed ia tes
Placido Neri,* Grazia M. L. Consoli, Francesca Cunsolo, Concetta Rocco, and Mario Piattelli
Istituto per lo Studio delle Sostanze Naturali di Interesse Alimentare e Chimico-Farmaceutico, C.N.R.,
Via del Santuario 110, I-95028 Valverde (CT), Italy
Received J anuary 3, 1997X
The behavior of a well-defined calix[8]arene trianion under alkylation conditions was investigated
by reacting the tetraethylammonium salt of p-tert-butylcalix[8]arene trianion with p-methylbenzyl
bromide. Chromatography of the reaction mixture afforded the following derivatives in order of
decreasing yields: 1,3,5,7-tetrakis-, 1,3-bis-, 1,3,5-tris-, 1,2,4-tris-, and mono(p-methylbenzyl)-p-
tert-butylcalix[8]arene, besides trace amounts of 1,4- and 1,5-disubstituted compounds. Comparable
results were obtained using p-tert-butylbenzyl bromide. The observed regioselectivity has been
explained by assuming that after each alkylation step the left negative charge is redistributed, by
exchange equilibria, over the remaining phenolic groups with preferential localization at those
positions where contiguous H-bond stabilization is possible and the electrostatic repulsion is
minimized. The occurrence of protonation/deprotonation equilibria allows the formation of 1,3,5,7-
tetrasubstituted calix[8]arene.
In tr od u ction
nature of the base has a strong effect in the product
distribution in the reactions leading to both calix[4]-
crown9 and calix[8]crown ethers.10
The behavior of calixarenes1 in the base-promoted
alkylation at the phenolic hydroxyls is a crucial aspect
of their chemistry, whose understanding is a premise for
better control of the reaction.2 In fact, it has been largely
demonstrated that the influence of the nature of the base
(cation identity and strength) is of paramount importance
in determining the stereo- and regiochemical outcome of
the reaction.3 Thus, calix[4]arenes often give preferen-
tially the tetrasubstituted cone or partial cone atropiso-
mers in the presence of NaH or, respectively, Cs2CO3,4
while in their partial alkylation the use of K2CO3 affords
selectively 1,3-disubstituted derivatives5 and that of NaH
the 1,2-regioisomers.6 Moreover, in the arylmethylation
of calix[6]arenes NaH leads to the preferential formation
of 1,2,4,5-tetrasubstituted and KH that of 1,4-disubsti-
tuted derivatives,2,7 while 1,2,3- or 1,3,5-trisubstitution
is observed with either K2CO3 or CsF.8 Analogously, the
In order to rationalize these data the factor to be
considered first is the nature of the base, since in the
presence of weak or strong bases monoanions or, respec-
tively, polyanions are preferentially produced, thus driv-
ing the reaction through diverse pathways with the
formation of variously substituted derivatives.3-6 Thus,
it is commonly agreed that, in the presence of CsF or K2-
CO3, calix[n]arenes originate monoanions3,5c which evolve
mainly in accordance to the so-called alternate alkylation
route.11 Differently, in the presence of strong bases
(hydroxides or hydrides) polyanions are usually formed12,13
whose evolution is not yet fully understood.2,4d,6,14 In
many instances even the level of deprotonation is unclear,
making immaterial any further argumentation.
In the case of calix[8]arenes we have demonstrated
that alkylation in the presence of weak bases is mainly
driven by the preferential formation of monoanions
* To whom correspondence should be addressed. Phone +39-95-
7212136; fax +39-95-7212141; e-mail neri@issn.ct.cnr.it.
X Abstract published in Advance ACS Abstracts, May 15, 1997.
(1) Gutsche, C. D. Calixarenes; Royal Society of Chemistry: Cam-
bridge, 1989. Calixarenes: A Versatile Class of Macrocyclic Compounds;
Vicens, J ., Bo¨hmer, V., Eds.; Kluwer: Dordrecht, 1991.
(2) Kanamathareddy, S.; Gutsche, C. D. J . Org. Chem. 1992, 57,
3160.
(8) Casnati, A.; Minari, P.; Pochini, A.; Ungaro, R. J . Chem. Soc.,
Chem. Commun. 1991, 1413. Moran, J . K.; Roundhill D. M. Inorg.
Chem. 1992, 31, 4213. J anssen, R. G.; Verboom, W.; Reinhoudt, D. N.;
Casnati, A.; Freriks, M.; Pochini, A.; Ugozzoli, F.; Ungaro, R.; Nieto,
P. M.; Carramolino, M.; Cuevas, F.; Prados, P.; de Mendoza, J .
Synthesis 1993, 380. Neri, P.; Rocco, C.; Consoli, G. M. L.; Piattelli,
M. J . Org. Chem. 1993, 58, 6535. Neri, P.; Consoli, G. M. L.; Cunsolo,
F.; Piattelli, M. Tetrahedron Lett. 1994, 35, 2795. Moran, J . K.;
Georgiev, E. M.; Yordanov, A. T.; Mague, J . T.; Roundhill D. M. J .
Org. Chem. 1994, 59, 5990.
(9) Yamamoto, H.; Sakaki, T.; Shinkai, S. Chem. Lett. 1994, 469.
(10) Geraci, C.; Piattelli, M.; Neri, P. Tetrahedron Lett. 1996, 37,
3899.
(11) Neri, P.; Geraci C.; Piattelli, M. J . Org. Chem. 1995, 60, 4126.
(12) Gutsche, C. D.; Iqbal, M.; Nam, K. C.; See, K. A.; Alam, I. Pure
Appl. Chem. 1988, 60, 483. Gutsche, C. D.; Alam, I.; Iqbal, M.;
Mangiafico, T.; Nam, K. C.; Rogers, J .; See, K. A. J . Inclusion Phenom.
1989, 7, 61.
(13) (a) Harrowfield, J . M.; Ogden, M. I.; Richmond, W. R.; Skelton,
B. W.; White, A. H. J . Chem. Soc., Perkin Trans. 2 1993, 2183. (b)
Danil de Namor, A. F.; Garrido Pardo, M. T.; Pacheco Tanaka, D. A.;
Sueros Velarde, F. J .; Ca´rdenas Garc´ıa, J . D.; Cabaleiro, M. C.; Al-
Rawi, J . M. A. J . Chem. Soc., Faraday Trans. 1993, 89, 2727. (c)
Tatezaki, T.; Hayashi, K.; Yoshida, I.; Sagara, F.; Ishii, D.; Ueno, K.;
Shinkai, S. Abstracts of 2nd Workshop on Calixarenes and Related
Compounds, Kurume (J apan), 2-4 J une 1993, PS/A-30. (d) Harrow-
field, J . M.; Richmond, W. R.; Sobolev, A. N. J . Inclusion Phenom. 1994,
19, 257.
(3) Shinkai, S. Tetrahedron 1993, 49, 8933. V. Bo¨hmer, Angew.
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(4) (a) Iwamoto, K.; Araki, K.; Shinkai, S. J . Org. Chem. 1991, 56,
4955. (b) Iwamoto, K.; Araki, K.; Shinkai, S. Tetrahedron 1991, 47,
4325. (c) Verboom, W.; Datta, S.; Asfari, Z.; Harkema, S.; Reinhoudt,
D. N. J . Org. Chem. 1992, 57, 5394. (d) Pappalardo, S.; Giunta, L.;
Foti, M.; Ferguson, G.; Gallagher, J . F.; Kaitner, B. J . Org. Chem. 1992,
57, 2611.
(5) (a) Gutsche, C. D.; Dhawan, B.; Levine, J . A.; No, K. H.; Bauer,
L. J . Tetrahedron 1983, 39, 409. (b) Dijkstra, P. J .; Brunink, J . A. J .;
Bugge, K.-E.; Reinhoudt, D. N.; Harkema, S.; Ungaro, R.; Ugozzoli,
F.; Ghidini, E. J . Am. Chem. Soc. 1989, 111, 7567. (c) van Loon, J .-D.;
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S.; Reinhoudt, D. N. J . Org. Chem. 1990, 55, 5639. (d) Collins, E. M.;
McKervey, M. A.; Madigan, E.; Moran, M. B.; Owens, M.; Ferguson,
G.; Harris, S. J . J . Chem. Soc., Perkin Trans. 1 1991, 3137.
(6) (a) Bottino, F.; Giunta, L.; Pappalardo, S. J . Org. Chem. 1989,
54, 5407. (b) Groenen, L. C.; Rue¨l, B. H. M.; Casnati, A.; Timmerman,
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N. Tetrahedron Lett. 1991, 32, 2675.
(7) Rogers, J . S.; Gutsche, C. D. J . Org. Chem. 1992, 57, 3152. Neri,
P.; Foti, M.; Ferguson, G.; Gallagher, J . F.; Kaitner, B.; Pons, M.;
Molins, M. A.; Giunta, L.; Pappalardo, S. J . Am. Chem. Soc. 1992, 114,
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S0022-3263(97)00029-7 CCC: $14.00 © 1997 American Chemical Society

Alkylation Products of a Calix[8]arene Trianion
J . Org. Chem., Vol. 62, No. 13, 1997 4237
stabilized by two flanking hydrogen bonds leading to
1,3,5,7-tetraalkyl derivatives.11,15 The use of strong bases
that should originate polyanions12,13 usually leads to
exhaustive substitution or, with limiting amounts of
electrophile, to complex mixtures. In these instances
either the level of deprotonation and/or the behavior of
the formed polyanion is unknown. The study of the
alkylation of a preformed, well-defined polyanion seems
to be the best way to solve these questions. In principle
it is expected that such a polyanion should behave
differently from a monoanion, probably giving rise to
products with different substitution patterns.
The preparation of a well-defined calix[8]arene poly-
anion has been described in a recent paper by Harrow-
field et al. who have shown that treatment of a solution
of p-tert-butylcalix[8]arene (1) in acetonitrile with aque-
ous tetraethylammonium hydroxide produces a triple
deprotonation leading in good yield to the easily crystal-
lized salt (Et4N+)3(13-).13a This appears an interesting
subject for the study of the behavior of a formally
noncoordinated calix[8]arene trianion in the presence of
alkylating agents. Thus, we decided to investigate this
reaction using p-methylbenzyl bromide as electrophile,
since various fully characterized p-methylbenzyl ethers
of p-tert-butylcalix[8]arene were available as reference
compounds for products identification.11
F igu r e 1. Exchange equilibrium for charge distribution for
calix[8]arene trianion 13-
.
Ch a r t 1
Resu lts a n d Discu ssion
The salt (Et4N+)3(13-), prepared by following the pro-
cedure of Harrowfield et al.,13a was purified by repeated
recrystallization from CH3CN. Its identification was
based on elemental analysis and 13C NMR spectroscopy,
while integration of the 1H NMR spectrum confirmed the
correct 3:1 cation to anion ratio.16 According to chemical
intuition and molecular mechanics calculations,17 the
negative charges in 13- should be preferentially located
at the 1,3,6 relative positions in order to achieve the
maximum hydrogen-bonding stabilization and minimum
electrostatic repulsion. However, the appearance of three
single resonances for the t-Bu, ArCH2Ar, and ArH groups
1
in the H NMR spectrum16 evidences that, in the NMR
time scale, the charge is equally distributed over the eight
phenolic groups.13 Therefore a fast exchange equilibrium
in the NMR time scale has to be accepted, as sketched
in Figure 1.
In order to investigate the behavior of calix[8]arene
trianion 13- under alkylation conditions, a sample of this
salt was dissolved in anhydrous THF/DMF (10:1 v/v) and
reacted with 10 equiv of p-methylbenzyl bromide at reflux
for 12 h. TLC analysis of the crude reaction mixture
revealed a pattern similar to that observed in the
alkylation of 1 catalyzed by weak bases,11 while column
chromatography gave the following compounds (isolated
yields): 2 (5%), 3 (17%), 6 (12%), 7 (7%), and 8 (26%),
(15) (a) Neri, P.; Geraci, C.; Piattelli, M. Tetrahedron Lett. 1993,
34, 3319. (b) Neri, P.; Battocolo, E.; Cunsolo, F.; Geraci, C.; Piattelli,
M. J . Org. Chem. 1994, 59, 3880. (c) Cunsolo, F.; Consoli, G. M. L.;
Piattelli, M.; Neri, P. Tetrahedron Lett. 1995, 36, 3751. (d) Consoli, G.
M. L.; Cunsolo, F.; Neri, P. Gazz. Chim. Ital. 1996, 126, 791.
(16) For completeness we report here the spectral data of the known
13a
salt (Et4N+)3(13-
)
(see Experimental Section).
(17) Full minimization (MacroModel V4.5 computer program) of the
five isomeric structures of 13- in a pleated-loop conformation, using
MM2 or Amber force-field with GB/SA model solvent (H2O or CHCl3),
always favored 1,3,6-trianion by more than 5 kcal/mol with respect to
the nearest higher energy isomer. The 1,3,6-charge localization in a
calix[8]arene trianion was first suggested by Shinkai and co-workers
(ref 13c).
besides trace amounts of 4 and 5 (Chart 1). Identification
was based on spectral comparison with authentic samples
available from previous work.11
Formation of 1,3,5-tri- and 1,3,5,7-tetrasubstituted
derivatives by alkylation of calix[8]arene trianion 13-

4238 J . Org. Chem., Vol. 62, No. 13, 1997
Neri et al.
compounds from the mixtures obtained by benzylation
of 1 in the presence of CsF or K2CO3 have been unsuc-
cessful because of their chromatographic overlapping
with other polybenzyl compounds.15b Two other com-
pounds were isolated in trace amounts for which, on the
1
basis of H NMR spectra, we suggest the structure of
1,3,5-tris(tert-butylbenzyl) derivative 6a and 1,2,4-tris-
(tert-butylbenzyl)calix[8]arene 7a . However, because of
their minimal amounts and impure form they were not
fully characterized.
In conclusion, the alkylation of a preformed and well-
defined calixarene polyanion here described may be
considered a general approach for a better understanding
of their chemistry and a procedure of some synthetic
utility. It has been evidenced that regioisomer distribu-
tion in the alkylation of a calix[8]arene trianion is similar
to that observed when a monoanionic pathway is active.
In the former instance, charge redistribution in inter-
mediate species and occurrence of protonation/deproto-
nation equilibria are key factors for product distribution.
The scope and extension of this approach to other calix-
[n]arene systems will be the subject of future studies.
F igu r e 2. Proposed alkylation pathway for calix[8]arene
trianion 13-
.
appears somewhat surprising at first sight, since these
compounds are characteristic products of the monoan-
ionic pathway. In order to rationalize how these com-
pounds are formed, we suggest the following mechanism.
The first alkylation step of 13- yields monoalkylated
dianionic species 22-, which very likely adopts a prefer-
ential 3,7-charge distribution (Figure 2) in order to reduce
electrostatic repulsion, with concomitant H-bond stabi-
lization by flanking OH groups. Further alkylation of
this dianion then originates the 1,3-dialkyl monoanion
3-, with the charge localized at either position 5 or 6. In
accordance with our previous study on the alternate
alkylation of 1, this intermediate gives preferentially the
1,3,5-trisubstituted derivative 6, besides a small amount
of 1,2,4-isomer 7.11
According to chemical knowledge, 1,3,5-triether 6
should be a stronger acid than the conjugated species of
13- or 22- and therefore it may undergo an acid-base
exchange with these anions still present in solution,
followed by an alkylation step to give the 1,3,5,7-
tetrasubstituted compound 8 (Figure 2). Of course,
during the reaction several intermolecular protonation/
deprotonation equilibria take place leading to a distribu-
tion from mono- to tetraalkylated products.18 However,
the observed regioselectivity indicates the preferential
localization of the charge, in all intermediate anionic
species, at those positions more stabilized by contiguous
H-bonds and with lower electrostatic repulsion.19
Exp er im en ta l Section
Gen er a l Com m en ts. Melting points are uncorrected.
NMR spectra were taken on a Bruker AC-250 spectrometer
operating at 250.13 (1H) and 62.9 (13C) MHz, using Me4Si as
internal standard. Elemental analyses were obtained from the
Dipartimento di Scienze Farmaceutiche of the University of
Catania. Column chromatography was performed using silica
gel (kieselgel 60, 63-200 µm, Merck). Preparative TLC
(PTLC) was carried out using silica gel plates (kieselgel 60
F254, 1 mm, Merck). All chemicals were reagent grade and
were used without further purification. Aqueous Et4NOH
(20%, w/v), anhydrous DMF, and THF were purchased from
Aldrich. p-tert-Butylcalix[8]arene (1) was prepared by a
literature procedure21 while reference samples of p-methyben-
zyl calix[8]arenes (2-8)11 and 1,3,5,7-tetrakis(p-tert-butylben-
zyl) ether 8a 15b were available from previous work.
P r ep a r a t ion of Tet r a et h yla m m on iu m Sa lt of p -ter t-
Bu tylca lix[8]a r en e (Et4N+)3(13-). (Et4N+)3(13-) was pre-
pared essentially according to the method of Harrowfield.13a
To a suspension of p-tert-butylcalix[8]arene (2.0 g, 1.54 mmol)
in CH3CN (40 mL) was added 20% (w/v) aqueous Et4NOH (12
mL), and the mixture was brought to reflux. While refluxing,
additional aliquots of Et4NOH were added until a clear
solution was observed. Upon standing overnight in a refrig-
erator, the crystalline precipitate was collected by filtration,
washed with cold CH3CN, and recrystallized (×3) to give pure
(Et4N+)3(13-) (0.70 g, 27%): 1H NMR (250.13 MHz, CDCl3, 340
K) δ 1.18 (t, J ) 6.8 Hz, 36 H), 1.26 (s, 72 H), 3.13 (q, J ) 6.8
Hz, 24 H), 3.90 (s, 16 H), 7.05 (s, 16 H); 13C NMR (62.9 MHz,
C5D5N, 296 K) δ 7.7 (q), 32.1 (q), 34.0 (t), 34.1 (s), 52.8 (t),
125.4 (d), 129.6 (s), 140.2 (s), 153.9 (s).
This consideration should be independent of the nature
of the electrophile,20 making this approach of considerable
usefulness from the synthetic point of view. Indeed,
extending this reaction to p-tert-butylbenzyl bromide we
isolated, besides to the expected 1,3,5,7-tetraether 8a 15b
(25%), the hitherto unknown mono(tert-butylbenzyl) de-
rivative 2a (30%) and 1,3-bis(tert-butylbenzyl)calix[8]-
arene 3a (33%). Their structures were readily assessed
on the basis of the same arguments used in previous work
for the structure assignments to 2 and 3.11 It is interest-
ing to observe that previous attempts at isolating these
Alk yla tion of (Et4N+)3(13-) w ith p-Meth ylben zyl Br o-
m id e. A solution of (Et4N+)3(13-) (350 mg, 0.21 mmol) and
p-methylbenzyl bromide (400 mg, 2.2 mmol) in THF/DMF (10:1
v/v, 22 mL) was refluxed for 12 h. Evaporation of the solvent
afforded a residue which was washed with 0.1 N HCl (30 mL)
followed by MeOH (8 mL) and dried. The crude product was
subjected to column chromatography (silica gel, elution with
increasing concentrations of CH2Cl2 in petroleum ether) and,
when needed, some of the pooled fractions were further
purified by PTLC to give (isolated yields) 2 (15 mg, 5%), 3 (54
mg, 17%), 6 (41 mg, 12%), 7 (24 mg, 7%), and 8 (94 mg, 26%).
(18) In principle, the occurrence of these equilibria could be dem-
onstrated by mixing the salt with 2, 3, or 6, while mathematical
modeling could lead to the determination of relative acidities. However,
these investigations remain beyond the purpose of the present work.
(19) It is worth mentioning that in the absence of preferential charge
localization a large number of all possible regioisomers should be
formed with a statistical distribution (one mono-, four di-, five tri-,
and eight tetrasubstituted derivatives).
Alk yla t ion of (E t4N+)3(13-) w it h p -ter t-Bu t ylb en zyl
Br om id e. p-tert-Butylbenzyl bromide (0,14 mL, 0.74 mmol)
was reacted, under conditions similar to those above, with
(20) However, it is to be expected that more reactive electrophiles
could react also with less stable anions with loss of regioselectivity.
(21) Munch, J . H.; Gutsche, C. D. Org. Synth. 1989, 68, 243.

Alkylation Products of a Calix[8]arene Trianion
J . Org. Chem., Vol. 62, No. 13, 1997 4239
(Et4N+)3(13-) (250 mg, 0.15 mmol) for 20 h. Purification by
column chromatography (silica gel, elution with increasing
concentrations of CH2Cl2 in petroleum ether) of the crude
product afforded 2a (64 mg, 30%), 3a (78 mg, 33%), and 8a
(70 mg, 25%).
5,11,17,23,29,35,41,47-Octa -ter t-bu tyl-49-[(4-ter t-bu tyl-
ben zyl)oxy]ca lix[8]a r en e-50,51,52,53,54,55,56-h ep tol (2a ):
mp > 400 °C dec; Rf 0.5 (CH2Cl2/petroleum ether, 2:3 v/v); 1H
NMR (250.13 MHz, C6D6, 350 K) δ 1.25, 1.26, 1.29, 1.33 (s, 27
H, 18 H, 9 H, 27 H, respectively), 3.75, 3.88, 3.97, 4.07 (s, 4 H
each), 4.86 (s, 2 H), 7.10-7.28 (overlapped, 14 H), 7.32 (s, 2
H), 7.68 and 7.73 (AB, J ) 8.7 Hz, 4 H); 13C NMR (62.9 MHz,
CDCl3, 310 K) δ 29.7 (t), 31.5 (q), 32.4, 32.6 (t), 34.0 (s), 78.1
(t), 125.2, 125.6, 125.8, 126.6 (d), 127.0, 127.6, 127.9, 128.1
(s), 128.7 (d), 133.0, 133.3, 143.1, 144.1, 144.5, 144.8, 146.7,
147.3, 148.7, 150.6 (s). Anal. Calcd. for C99H126O8: C, 82.34;
H, 8.79. Found: C, 82.19; H, 8.90.
5,11,17,23,29,35,41,47-Octa -ter t-bu tyl-49,51-bis[(4-ter t-
bu tylben zyl)oxy]calix[8]ar en e-50,52,53,54,55,56-h exol (3a):
mp 163-165 °C; Rf 0.45 (CH2Cl2/petroleum ether, 2:3 v/v); 1H
NMR (250.13 MHz, C6D6, 340 K) δ 1.13, 1.30, 1.31, 1.38, 1.40
(s, 18 H, 18 H, 27 H, 18 H, 9 H, respectively), 3.93, 4.00, 4.22
(s, 8 H, 4 H, 4 H, respectively), 4.84 (s, 4 H), 7.16 (d, J ) 2.3
Hz, 2 H), 7.17 (d, J ) 2.3 Hz, 2 H), 7.19-7.28 (overlapped, 10
H), 7.29 (d, J ) 2.2 Hz, 2 H), 7.39 and 7.46 (AB, J ) 8.3 Hz,
8 H); 13C NMR (62.9 MHz, CDCl3, 310 K) δ 29.7 (t), 31.3, 31.5
(q), 32.0, 32.1, 32.4 (t), 34.0, 34.3, 34.7 (s), 77.7 (t), 124.3, 125.1,
125.4, 125.6, 125.7 (d), 126.0 (s), 126.3, 126.8 (d), 127.0, 127.8,
128.0, 128.4 (s), 128.7(d), 132.0, 132.9, 133.0, 141.9, 143.1,
144.1, 144.4, 146.8, 147.1, 147.7, 149.0, 150.4, 151.0, 151.8 (s).
Anal. Calcd for C110H140O8: C, 83.08; H, 8.87. Found: C,
82.98; H, 9.02.
J O970029U