Practical partial synthesis of myriceric acid A, an endothelin receptor antagonist, from oleanolic acid

Article abstract of DOI:10.1021/jo9615864

Myriceric acid A (1) is an oleanane triterpene that is a potent and specific endothelin A receptor antagonist. A practical procedure for large-scale synthesis of myriceric acid A (1) has been developed starting from oleanolic acid 4. The conversion of oleanolic acid 4 to the key intermediate myricerone 3 was achieved in an efficient manner employing a photochemical reaction (the Barton reaction) of nitrite 7. Our synthetic procedure alleviated several difficulties of the original Barton's procedure with regard to yields and large-scale operation. Myricerone 3 afforded Horner-Wadsworth-Emmons (HWE) type phosphonate 2 which has proved to be a versatile precursor of 1. The preparation of phosphonate 2 on a scale of several hundred grams is described. The synthesis was completed by condensation of 2 with 3,4-bis[(diphenylmethyl)oxy]benzaldehyde (21), giving α,β-unsaturated ester 22, which was deprotected to afford 1. The whole synthetic sequence is efficient (14 steps, 31% yield) and requires no chromatographic purification except to obtain the final product 1.

Full text of DOI:10.1021/jo9615864

960
J . Org. Chem. 1997, 62, 960-966
P r a ctica l P a r tia l Syn th esis of Myr icer ic Acid A, a n En d oth elin
Recep tor An ta gon ist, fr om Olea n olic Acid
Toshiro Konoike,* Kazuhiro Takahashi, Yoshitaka Araki, and Isao Horibe
Shionogi Research Laboratories, Shionogi & Co., Ltd., Fukushima-ku, Osaka 553, J apan
Received August 15, 1996X
Myriceric acid A (1) is an oleanane triterpene that is a potent and specific endothelin A receptor
antagonist. A practical procedure for large-scale synthesis of myriceric acid A (1) has been developed
starting from oleanolic acid 4. The conversion of oleanolic acid 4 to the key intermediate myricerone
3 was achieved in an efficient manner employing a photochemical reaction (the Barton reaction) of
nitrite 7. Our synthetic procedure alleviated several difficulties of the original Barton’s procedure
with regard to yields and large-scale operation. Myricerone 3 afforded Horner-Wadsworth-
Emmons (HWE) type phosphonate 2 which has proved to be a versatile precursor of 1. The prepara-
tion of phosphonate 2 on a scale of several hundred grams is described. The synthesis was completed
by condensation of 2 with 3,4-bis[(diphenylmethyl)oxy]benzaldehyde (21), giving R,â-unsaturated
ester 22, which was deprotected to afford 1. The whole synthetic sequence is efficient (14 steps,
31% yield) and requires no chromatographic purification except to obtain the final product 1.
Sch em e 1
In tr od u ction
Myriceric acid A (27-(caffeoyloxy)-3-oxoolean-12-en-28-
oic acid) (1)1 is a potent and specific endothelin A receptor
antagonist2 that was found by screening of the Shionogi
natural product library and was isolated from a crude
extract of twigs of the southern bayberry, Myrica cerifera.
It is an oleanane triterpene that characteristically bears
3-oxo- and 27-caffeoyloxy-groups. It showed a promising
hypotensive effect for therapeutic use in animal tests.3
However, it was difficult to provide a sufficient amount
of 1 for further pharmacological evaluation and study of
structure-activity relationships of its derivatives, be-
cause of the scarcity of the plant in J apan and the low
content of 1 in the plant (0.01%). To overcome this
obstacle, we have developed a highly efficient and practi-
cal synthesis of 1 from naturally abundant oleanolic acid
4. We herein report the details of this study.
Resu lts a n d Discu ssion
27-O-acylation owing to a concurrent formation of a
mixed anhydride between the 28-carboxy group and an
acylating reagent. Consequently, this required a mild
alkaline workup to hydrolyze the mixed anhydride and
chromatographic separation of the 27-O-acyloxy product
from the excess acylating reagent. Moreover, we failed
to prepare 1 by acylating 3 with 3,4-di-O-acetylcaffeic
acid. In order to synthesize 1, we developed a new
synthetic procedure which employs a Horner-Wad-
sworth-Emmons (HWE) olefination4 of crystalline 27-
O-[(diethylphosphono)acetyl]myricerone (2) with a dihy-
droxybenzaldehyde derivative. HWE condensation of
phosphonate 2 occurred with a variety of aldehydes to
give R,â-unsaturated esters in good yields.
The retrosynthetic analysis of 1 is illustrated in
Scheme 1. We planned to prepare 1 via two key
intermediates 2 and 3. Our previous paper1 described
alkaline hydrolysis of the 27-caffeoyloxy group of 1 to give
myricerone (3) and its subsequent acylation to 27-O-
acylmyricerone. We prepared either the acetate or
cinnamate of 3 in a moderate yield by acylation of 3 with
acid chlorides or anhydrides, and 27-O-cinnamoylmyricero-
ne was shown to be as potent as 1 among the synthetic
27-O-acyl derivatives. However, acylation of 3 was
generally inefficient for several reasons. More than 3
equiv of acylating reagent was necessary to complete the
X Abstract published in Advance ACS Abstracts, February 1, 1997.
(1) Sakurawi, K.; Yasuda, F.; Tozyo, T.; Nakamura, M.; Sato, T.;
Kikuchi, J .; Terui, Y.; Ikenishi, Y.; Iwata, T.; Takahashi, K.; Konoike,
T.; Mihara, S.; Fujimoto, M. Chem. Pharm. Bull. 1996, 44, 343.
(2) For endothelins and their receptor antagonists, see Cheng, X.-
M.; Nikam, S. S.; Doherty, A. M. Curr. Med. Chem. 1994, 1, 271.
Doherty, A. M. Drug Discovery Today 1996, 1, 60. Ohlstein, E. H.;
Elliott, J . D.; Feuerstein, G. Z.; Ruffolo, R. R. Med. Res. Rev. 1996, 16,
365.
(3) Fujimoto, M.; Mihara, S.; Nakajima, S.; Ueda, M.; Nakamura,
M.; Sakurai, K. FEBS Lett. 1992, 305, 41. Mihara, S.; Fujimoto, M.
Eur. J . Pharmacol. 1993, 246, 33. Mihara, S.; Sakurai, K.; Nakamura,
M.; Konoike, T.; Fujimoto, M. Eur. J . Pharmacol. 1993, 247, 219.
As myricerone 3 was an apparent intermediate to 1,
we next focused on the synthesis of 3 from a readily
available compound. Oleanolic acid (4)5 has a very close
(4) For a review, see Maryanoff, B. E.; Reitz, A. B. Chem. Rev. 1989,
89, 863.
(5) For a review of recent work on oleanane and related triterpenes,
see Connolly, J . D.; Hill, R. A.; Ngadjui, B. T. Nat. Prod. Rep. 1994,
11, 467. For 27-caffeoyloxy oleananes, see J iang, Z.-H.; Tanaka, T.;
Kouno, I. Tetrahedron Lett. 1994, 35, 2031, J iang, Z.-H.; Tanaka, T.;
Kouno, I. Chem. Pharm. Bull. 1996, 44, 1669.
S0022-3263(96)01586-1 CCC: $14.00 © 1997 American Chemical Society

Partial Synthesis of Myriceric Acid A
J . Org. Chem., Vol. 62, No. 4, 1997 961
Sch em e 2
Ta ble 1. P r od u ct Ra tio of th e P h otoch em ica l Rea ction
structure to 3, and all that is required to convert 4 to 3
is oxidation of the 3-hydroxy to the 3-oxo group and
hydroxylation of the methyl group at the 27-position.
Barton and co-workers6 reported a synthesis of cincholic
acid (3â-hydroxyolean-12-ene-27,28-dioic acid) three de-
cades ago, which started from oleanolic acid (4) and
introduced a hydroxy group at the 27-position by a
photochemical reaction known as the Barton reaction.7
Their method is in principle applicable to the synthesis
of 3, but it had some disadvantages including a number
of low-yielding steps as well as the need for extensive
chromatographic purification of the intermediates. Con-
sequently, the overall yield of the final cincholic acid
was much less than 1%. Thus, we modified the entire
sequence of reactions and established a practical method
suitable for large-scale synthesis of 1 without the need
of chromatographic purification of the intermediates
except for the final product 1.
Our synthesis of 1 is shown in Schemes 2-4. J ones
oxidation of oleanolic acid (4) gave oleanonic acid (5)8 that
has the same oxidation level at the 3-position as myricero-
ne. The second oxidation, 27-hydroxylation, required a
multistep conversion and began with introduction of the
12R-hydroxy group, a scaffold for the Barton reaction.
Ozone was introduced to a solution of crude 5 to give 12R-
hydroxy lactone 69 as a major product with a small
amount (6-7%) of 12-oxolactone 10,10 which can be
removed by crystallization of 6. Ozone oxidation11 for
generating 12R-hydroxy lactone 6 was more satisfactory
than m-CPBA oxidation6,12 that needs a large excess of
m-CPBA, a longer reaction time, and chromatographic
purification of 6. This two-step oxidation of 4 to 6 also
worked well for crude material 4 contaminated with
isomeric ursolic acid (ca 2%), and 6 was obtained easily
in a pure form by crystallization. Hydroxy lactone 6 was
product ratio (%)a
concentration
(mM)
pyridine
(equiv to 7)
solvent
8
9
10
6
others
acetone
toluene
CH2Cl2
THF
acetone
acetone
acetone
acetone
acetone
acetone
acetone
acetoneb
67
67
67
67
33
16
33
33
33
33
33
33
0.2
0.2
0.2
0.2
0.2
0.2
0
0.05
0.1
0.5
69
53
59
24
78
82
81
80
78
64
1
2
4
1
22
18
25
5
24
11
41
6
1
0
1
19 15
1
1
1
2
6
4
9
14
12
13
12
13
17
1
5
1
4
1
2
1
3
1
10
7
0.2 of NEt3 72
0.2
2
10 10
15
0
61
2
22
a
Total peak area of the products is 100%. The ratio was
calculated based on the UV absorbency (ꢀ) at 197 nm of each
b
product. Reaction was carried out under an oxygen atmosphere.
converted to nitrite 7 by treatment with nitrosyl chloride
in pyridine, and the unstable nitrite 7 was isolated by
conducting the workup and crystallization in a presence
of pyridine.13
Irradiation of nitrite 7 lead to several byproducts along
with the desired oxime 8.14 They were identified as the
parent hydroxy lactone 6, its oxidized ketone 10, and
nitrate 9.15 We surveyed the conditions for the Barton
reaction of 7 using a variety of solvents, temperature,
concentration, additives, and wavelength, and the results
are summarized in Table 1. The yields of the products
were determined by HPLC after thermally decomposing
the nitrosodimer to monomeric oxime 8. The mechanism
of the Barton reaction has been investigated exten-
sively,14,16,17 and most of our findings are in accord with
the previous observations. However, we did not detect
nitrimine 116 or cyclic ether 1214 which are often observed
as byproducts in the Barton reaction. Some significant
observations of the photoreaction are as follows: acetone
is the solvent of choice in terms of the yield of 8. Starting
material concentration is important, with the yield of 8
(6) Barton, D. H. R.; Sammes, P. G.; Silva, M. Tetrahedron, Suppl.
1966, 7, 57.
(7) Barton, D. H. R. Pure Appl. Chem. 1968, 16, 1.
(8) Savoir, R.; Ottinger, R.; Tursch, B.; Chiurdoglu, G. Bull. Soc.
Chim. Belg. 1967, 76, 335.
(9) Poehland, B. L.; Carte, B. K.; Francis, T. A.; Hyland, L. J .;
Allaudeen, H. S.; Troupe, N. J . Nat. Prod. 1987, 50, 706.
(10) Snatzke, G.; Elgamal, M. H. A. Liebigs Ann. Chem. 1972, 758,
190.
(11) Boar, R. B.; Knight, D. C.; McGhie, J . F.; Barton, D. H. R. J .
Chem. Soc. (C) 1970, 678. Boar, R. B.; J oukhadar, L.; Luque, M.;
McGhie, J . F.; Barton, D. H. R.; Arigoni, D.; Brunner, H. G.; Giger, R.
J . Chem. Soc., Perkin Trans. 1 1977, 2104.
(13) Barton, D. H. R.; Basu, N. K.; Day, M. J .; Hesse, R. H.; Pechet,
M. M.; Starratt, A. N. J . Chem. Soc., Perkin Trans. 1 1975, 2243.
(14) Barton, D. H. R.; Hesse, R. H.; Pechet, M. M.; Smith, L. C. J .
Chem. Soc., Perkin Trans. 1 1979, 1159.
(15) Allen, J .; Boar, R. B.; McGhie, J . F.; Barton, D. H. R. J . Chem.
Soc., Perkin Trans. 1 1973, 2402. Barton, D. H. R.; Day, M. J .; Hesse,
R. H.; Pechet, M. M. J . Chem. Soc., Perkin Trans. 1 1975, 2252.
(16) Nickon, A.; Ferguson, R.; Bosch, A.; Iwadare, T. J . Am. Chem.
Soc. 1977, 99, 4518.
(17) Burke, S. D.; Silks, L. A.; Strickland, S. M. S. Tetrahedron Lett.
1988, 29, 2761.
(12) Barton, D. H. R.; Holness, N. J . J . Chem. Soc. 1952, 78.

962 J . Org. Chem., Vol. 62, No. 4, 1997
Konoike et al.
Sch em e 3
rising as the concentration decreased, and we chose the
concentration of 67 mM as a compromise between the
yield and operational practicality. Exclusion of oxygen
is essential for preventing formation of nitrate 9, with
either an argon or nitrogen providing the best result.
When the photoreaction was carried out in an oxygen
atmosphere, nitrate 9 was obtained15 in 61% yield instead
of oxime 8. An additive such as pyridine13 was not
essential for the Barton reaction itself; however, it
prevented decomposition of 7 throughout the recrystal-
lization and photoreaction. Addition of pyridine (0.05-
0.2 equiv to 7) was beneficial when the photoreaction
period exceeded 1 h. Irradiation at 329-379 nm was
most effective. The reaction temperature had no signifi-
cant influence in the range of 0-30 °C, but 7 precipitated
below 0 °C. On the basis of these results, we ran the
photochemical reaction under the conditions where 7 was
consumed in less than 1 h, and oxime 8 was obtained as
a white crystalline powder in 69-85% yield (94-98%
purity by HPLC) from 6 in a 20 g scale preparation.
competing oxidation at the 2-position and the main
product 12 was contaminated with a significant amount
of 2-acetoxylated 6 and 12. The resulting cyclic ether
12 was resistant to ring-opening reaction under a variety
of conditions, and we did not pursue further conversion
of 12.
Barton et al. reported that a conversion of oxime 8 to
aldehyde 15 was very difficult due to the extreme steric
hindrance around the 27-position.6 They proposed sev-
eral methods for generating hydroxy aldehyde 15, which
were not practical for synthetic purposes. This led us to
a new method of generating an aldehyde that utilizes an
efficient three-step procedure via imine 13 (Scheme 3).
Oxime 8 was reduced to imine 13 in the first step by
treatment with TiCl3,19 and imine 13 was subsequently
hydrolyzed to aldehyde in a two-step sequence. Upon
treatment with NaNO2 in aqueous dioxane-acetic acid,
a 2:1 mixture of hydroxy aldehyde 15 and hemiacetal
acetate 14 was obtained. Alkaline hydrolysis of the
mixture provide aldehyde 15 as a sole product in 77%
yield from oxime 8. Imine 13 was stable under usual
hydrolysis conditions, but underwent sodium cyanoboro-
hydride reduction in acetic acid to give the 27-amino
compound. A similar amine was reported to be generated
from a nitrimine by catalytic hydrogenation or zinc-
acetic acid reduction;6 however, when we tried catalytic
hydrogenation of nitrimine 11 prepared from oxime 8,
we obtained imine 13 quantitatively instead of the 27-
amino compound.
The completion of the synthesis of myricerone 3 from
15 was accomplished as described in Scheme 3. The
3-oxo group of hydroxy aldehyde 15 was first protected
as an ethylene ketal 16, and then the 12-hydroxy group
was acetylated to give acetoxy ketal 17 (96% from 15).
Reductive elimination of the acetoxy lactone moiety of
17 occurred efficiently under the lithium-liquid am-
monia reduction to give quantitatively myricerone eth-
ylene ketal 18. Concomitant reduction of 27-aldehyde
to an alcohol was convenient for synthesis of myricerone
3. The ethylene ketal of 18 was deprotected by aqueous
HCl, and myricerone 3 was obtained as a crystalline
powder in 99% yield from 17. Myricerone 3 thus obtained
was sufficiently pure for practical synthesis, although it
We tried another type of remote oxidation, the hy-
poiodite reaction,18 often referred to as the Heusler
reaction. Under typical conditions, 6 was treated with
Pb(OAc)4, I2, and CaCO3 under irradiation from a tung-
sten lamp at room temperature, and cyclic ether 12 was
obtained in 70% yield. Unfortunately, the photoreaction
was not amenable to large-scale. However, we discovered
the reaction could be performed at room temperature
with sonication, and ether 12 was obtained in 60% yield.
Moreover, when the reaction was carried in toluene at
reflux without irradiation, we found that there was a
(18) Heusler, K.; Kalvoda, J . Angew. Chem., Int. Ed. Engl. 1964, 3,
525. Heusler, K.; Kalvoda, J . In Organic Reaction in Steroid Chemistry;
Fried, J ., Edward, J . A., Eds.; Van Noustrand Reinhold: New York,
1972; Vol. 2, chapter 12.
(19) Timms, G. H.; Wildsmith, E. Tetrahedron Lett. 1971, 2, 195.

Partial Synthesis of Myriceric Acid A
J . Org. Chem., Vol. 62, No. 4, 1997 963
Ta ble 2. Effect of Su bstitu en ts on 12,13-Olefin
Regen er a tion
contained a small amount of incompletely reduced byprod-
uct 19 (2%), which could be removed from 3 by recrys-
tallization. Myricerone 3 prepared as above was identical
with an authentic sample prepared by alkaline hydrolysis
of natural 1.1
Barton et al.6 showed the regeneration of the 12,13
double bond of oleanolic acid derivatives was severely
limited and low yielding. In contrast, the regeneration
of the double bond from 17 was very facile, and we
assumed that a substituent at the 27-position affected
the efficiency of the olefin regeneration. In order to
examine the substituent effect of the 27-position, we
carried out the olefin regeneration using several related
substrates bearing several 27- and 3-substituents. Our
results as well as Barton’s demonstrate that the reaction
is sensitive to the substituent at the 27-position rather
than the 3-position (Table 2). Efficient conversion of the
substrates having the 27-aldehyde group was noteworthy.
Our conjecture on the mechanism is as follows. The
reductive elimination initially involves an electron trans-
fer from lithium to the aldehyde group which is more
electron-deficient than other groups. The resulting radi-
cal anion of the aldehyde effectively transfers an electron
to the nearby 12R-acetoxy group, accelerating the reduc-
tive elimination of the acetoxy group and the lactone. The
electron transfer mechanism is verified experimentally.
Olefin aldehyde 19 was generally obtained as a byproduct
after deketalization, and this implied that 19 was a
primary product of the reduction. As an additional
evidence, when the lithium-liquid ammonia reduction
was done in a more concentrated solution, we obtained
dimeric diol 20 together with myricerone (3) and alde-
hyde 19 after deketalization. The generation of diol 20
demonstrated the dimerization of a radical anion of the
ethylene ketal of 19. All these results suggest that the
electron transfer to the aldehyde is a favorable process,
and it facilitates the electron transfer to acetoxy group
and the subsequent olefin regeneration.
eric acid A (1) was not obtained, and only starting
materials were recovered. This was presumably because
ionization of the phenolic OH group deactivated the
aldehyde for HWE olefination. To prevent the inactiva-
tion we employed the diphenymethyl group as a protect-
ing group of phenol,20 and 3,4-bis[(diphenylmethyl)oxy]-
benzaldehyde (21) was prepared by alkylating 3,4-
dihydroxybenzaldehyde with bromodiphenylmethane
(Scheme 4). Condensation21 of 2 with 21 proceeded to
give 22 quantitatively. Deprotection of the diphenym-
ethyl group by trifluoroacetic acid-anisole gave myriceric
acid A (1) which was identical to an authentic sample
isolated from M. cerifera. The whole series of conversions
gave high yields and 1 was obtained from oleanolic acid
(4) in 14 steps in 31% yield.
Intermediate 2 is a more versatile intermediate than
myricerone 3 for modification studies of 1 because it can
be condensed with a variety of aldehydes to give R,â-
unsaturated acyloxy derivatives in a single step. These
derivatives enabled us to study their structure-activity
relationships. From these studies, more potent and
water-soluble derivatives were found. We have prepared
several kilograms of 2 and a drug candidate22 for further
pharmacological evaluation.
Exp er im en ta l Section
Gen er a l. Reactions were carried out under a nitrogen
atmosphere in anhydrous solvents (dried over molecular sieves
type 4A). Organic extracts were dried over anhydrous MgSO4.
Solvent removal was accomplished under aspirator pressure
using a rotary evaporator. TLC was performed with Merck
precoated TLC plates silica gel 60 F254, and compound visu-
alization was effected with 10% H2SO4 containing 5% am-
monium molybdate and 0.2% ceric sulfate. Gravity chroma-
tography was done with Merck silica gel 60 (70-230 mesh).
HPLC analysis was performed under the conditions; column,
Acylation of myricerone 3 by 3,4-di-O-acetylcaffeoyl
chloride only gave 27-O-acetylmyricerone and none of a
caffeoyl derivative. We therefore devised an alternative
HWE olefination employing phosphonate 2 for the prepa-
ration of myriceric acid A (1). Myricerone 3 was con-
densed with commercially available diethoxyphospho-
noacetic acid by carbonyldiimidazole to give crystalline
phosphonate 2. The synthetic sequence from 4 was very
efficient and phosphonate 2 could be prepared on a scale
of several hundred grams (12 steps, 39% yield) without
chromatographic purification of the intermediates.
To complete the partial synthesis of myriceric acid A
(1), we attempted to condense 2 with 3,4-dihydroxyben-
zaldehyde under several basic conditions; however, myric-
(20) Dobson, D; Todd, A.; Gilmore, J . Synth. Commun. 1991, 21,
611.
(21) Blanchette, M. A.; Choy, W.; Davis, J . T.; Essenfeld, A. P.;
Masamune, S.; Roush, W. R.; Sakai, T. Tetrahedron Lett. 1984, 25,
2183.
(22) Mihara, S.; Nakajima, S.; Matsumura, S.; Konoike, T.; Fujimoto,
M. J . Pharmacol. Exp. Ther. 1994, 268, 1122.

964 J . Org. Chem., Vol. 62, No. 4, 1997
Konoike et al.
(s, 3), 1.32 (s, 3), 1.2-1.8 (m, 14), 1.8-2.2 (m, 8), 2.39 (dd, 2,
J ) 11.9, 2.5), 2.4-2.55 (m, 2), 2.79 (t, 1, J ) 14.2). Anal.
Calcd for C30H44O4: C, 76.88; H, 9.46. Found: C, 76.58; H,
9.28.
Sch em e 4
La cton e Nitr ite 7. A stream of NOCl, generated from
NaNO2 (87.4 g) and 35% HCl (509 mL), was introduced to an
ice-cold solution of 6 (298 g, 0.634 mol) in pyridine (3 L) at
-40 °C over 30 min. The mixture was stirred at -40 °C for
30 min and poured into ice-water (4.4 L). The resulting
precipitate was collected by filtration and washed with H2O
(2.5 L). The wet precipitate was dissolved in CH2Cl2/pyridine
(2.9 L/52 mL), and the organic layer was separated and
concentrated. The residue was triturated with hexane (1.2 L),
and the white powder was filtered and washed with hexane
(0.5 L) to give 7 as a white powder (296 g, 94%). Mp 254-258
°C dec. TLC (CH2Cl2/EtOAc (8/1)) Rf 0.68. HPLC (MeCN/H2O/
AcOH (80/20/0.1)) tR 27.1 min. IR (CHCl3): 2955, 1760, 1699
cm-1 1H NMR: δ 0.75 (s, 3), 0.93 (s, 3), 0.99 (s, 3), 1.04 (s, 3),
.
1.09 (s, 3), 1.16 (s, 3), 1.26 (s, 3), 1.2-1.7(m, 13), 1.7-2.3 (m,
8), 2.3-2.5 (m, 2), 5.64 (dd, 1, J ) 3.5, 2.0). Anal. Calcd for
C30H45NO5: C, 72.11; H, 9.08; N, 2.80. Found: C, 72.06; H,
9.20; N, 2.85.
Cosmosil 5C18 AR 4.6 mm × 150 mm; guard column, Lichro-
spher 100 RP 18; solvent, MeCN/H2O/AcOH (70/30/0.1) if not
specified; flow rate, 1 mL/min; detection, 197 nm. Melting
points are uncorrected. 1H NMR and 13C NMR spectra were
determined as CDCl3 solutions at 200 and 50.3 MHz. J values
are given in hertz. High-resolution mass spectra (HR-LSIMS)
were recorded on a Hitachi M-90 instrument.
P h otoch em ica l Rea ction of 7. The photoreaction condi-
tions were surveyed using a variety of solvents, concentrations,
temperatures, wavelengths, and additives. Each photoreaction
mixture was heated under reflux in dichloroethane to decom-
pose the primary photoproduct, nitroso dimer, and the com-
position of the products was monitored by TLC and HPLC. Rf
and tR of starting nitrite 7 and four major products are as
follows: TLC (CH2Cl2/EtOAc (10/1)): Rf oxime 8 (0.1), nitrate
9 (0.6), hydroxy 6 (0.4), ketone 10 (0.7), nitrite 7 (0.85).
HPLC: tR (min), oxime 8 (3.6), nitrate 9 (7.7), hydroxy 6 (11.8),
ketone 10 (12.9), nitrite 7 (27.1).
Olea n on ic Acid (3-Oxoolea n -12-en -28-oic a cid ) (5). A
suspension of oleanolic acid (4) isolated from olive leaves (200
g, 0.44 mol) in 2 L of CH2Cl2/acetone (1/1) was cooled to 5 °C,
and a solution of J ones reagent (200 mL, 1.2 equiv) was added
dropwise over 30 min maintaining the temperature at 5 °C,
and the mixture was stirred for an additional 15 min. To the
reaction mixture were added i-PrOH (100 mL) and H2O (400
mL), and the resulting mixture was stirred at room temper-
ature for 10 min. Water (3 L) and CH2Cl2 (2 L) were added to
the mixture and the layers separated. The organic layer was
washed with saturated NaCl (2 L), dried, and concentrated to
2.1 kg to give a CH2Cl2 solution of oleanonic acid 5, which was
ozonized in the next step. Pure oleanonic acid 5 was obtained
by silica gel chromatography of a small aliquot of the extract
and subsequent crystallization. Needles (MeOH), mp 178-
Twenty gram-scale preparation was performed by irradiat-
ing a solution of 7 (20 g, 40 mmol) in acetone (1.2 L) containing
a small amount of pyridine (0.16 mL) with a high pressure
Hg lamp (400 W) through a Pyrex filter under nitrogen
atmosphere for 1 h. Fourteen batches of the photoreaction
mixture were combined and concentrated (324 g). 1,2-Dichlo-
roethane (1.4 L) was added to the residue, and the solution
was refluxed for 1.5 h. The resulting slurry was collected by
filtration and washed with dichloroethane (300 mL) to give 8
as white crystals (206 g, 74%). The filtrate was concentrated
to 1.2 kg, and an additional amount of 8 (31 g, 11%, total yield
85%) was obtained as a crystalline powder: mp 285-289 °C
dec. TLC (CH2Cl2/EtOAc (8/1)) Rf 0.16. IR (CHCl3): 3574,
179 °C. [R]24 +96.9° (c 1.506, CHCl3) [lit.8 mp 226-229 °C.
D
[R]22 +98° (c 0.935, CHCl3)]. TLC (hexane/EtOAc (2/1)) Rf
D
0.51. 1H NMR: δ 0.81 (s, 3), 0.91 (s, 3), 0.93 (s, 3), 1.03 (s, 3),
1.05 (s, 3), 1.09 (s, 3), 1.15 (s, 3), 1.2-2.1 (m, 21), 2.3-2.7 (m,
2), 2.75-2.90 (br s, 1), 5.31 (br s, 1). 13C NMR: δ 15.0, 17.0,
19.5, 21.4, 22.9, 23.5, 23.6, 25.8, 26.4, 27.7, 30.7, 32.2, 32.4,
33.1, 33.8, 34.1, 36.8, 39.1, 39.3, 41.0, 41.7, 45.8, 46.6, 46.9,
47.4, 55.3, 122.3, 143.7, 184.4, 217.5. Anal. Calcd for
C30H46O3: C, 79.25; H, 10.20. Found: C, 79.01; H, 10.21.
LSIMS m/ z 455 [M + H]+.
3308, 3016, 2955, 2869, 1768, 1699 cm-1 1H NMR: δ 0.90 (s,
.
3), 0.95 (s, 3), 0.98 (s, 3), 1.03 (s, 3), 1.07 (s, 3), 1.26 (s, 3),
1.2-1.8 (m, 13), 1.8-2.2 (m, 8), 2.2-2.4 (m, 2), 3.88 (d, 1, J )
6.0), 4.20 (d, 1, J ) 6.0), 7.62 (s, 1), 8.12 (s, 1). 13C NMR: δ
16.7, 18.1, 18.9, 21.0, 24.2, 24,6, 26.9, 27.1, 28.4, 31.4, 33.1,
33.8, 34.0, 35.4, 36.4, 39.0, 39.5, 42.9, 43.5, 44.2, 45.0, 47.3,
48.8, 50.2, 54.6, 75.1, 88.6, 156.8, 179.2, 218.1. [R]23.5D +48.9°
(c 1.004, CHCl3). Anal. Calcd for C30H45NO5: C, 72.11; H,
9.08; N, 2.80. Found: C, 72.11; H, 9.08; N, 2.80. LSIMS m/ z
500 [M + H]+.
12r-Hyd r oxy-3-oxoolea n a n o-28,13-la cton e 6. To the
resulting solution of oleanonic acid (5) was added MeOH (200
mL), and ozone gas was introduced at -50 °C until 5 was not
detected on TLC. After removing excess ozone by bubbling
with N2 stream, the solution was concentrated to 0.4 kg, and
i-PrOH (150 mL) was added. The resulting crystalline product
was collected by filtration and washed with i-PrOH to give 6
Nitr a te 9. A solution of 7 (1 g, 2 mmol) and pyridine (0.032
mL, 0.4 mmol) in acetone (120 mL) was irradiated by high
pressure Hg lamp under O2 bubbling for 30 min. After
condensing the mixture, i-PrOH (2 mL) was added, and the
resulting precipitate was collected to give nitrate 9 (437 mg,
41%). Mp 221-222 °C. IR (CHCl3): 3410, 1767, 1699, 1631,
(163.3 g, 79%). Mp (MeOH) 283-285 °C dec. [R]23.5 +63.6°
D
(c 1.001, CHCl3) [lit.9 mp 304-306 °C, [R]23.5 +60.4° (c 1.08,
D
CHCl3)]. TLC (CH2Cl2/EtOAc (8/1)) Rf 0.34. HPLC tR 10.5
min. IR (CHCl3): 3619, 2955, 1760, 1699 cm-1 1H NMR: δ
.
1278 cm-1 1H NMR: δ 0.92 (s, 3), 0.98 (s, 3), 1.00 (s, 3), 1.05
.
0.91 (s, 3), 0.99 (s, 6), 1.05 (s, 3), 1.10 (s, 3), 1.19 (s, 3), 1.32 (s,
3), 1.2-1.8 (m, 14), 1.8-2.2 (m, 8), 2.44-2.55 (m, 2), 3.91 (br
s, 1). 13C NMR: δ 16.3, 18.2, 18.4, 19.1, 21.1, 21,2, 23.9, 26.7,
27.5, 28.0, 29.2, 31.6, 33.3, 33.4, 34.0, 34.1, 36.2, 39.5, 39.6,
42.2, 43.8, 44.7, 47.4, 51.2, 54.8, 76.2, 90.6, 179.8, 217.7. Anal.
Calcd for C30H46O4: C, 76.55; H, 9.85. Found: C, 76.22; H,
9.81. LSIMS m/ z 471 [M + H]+.
3,12-Dioxoolea n a n o-28,13-la cton e 10. The title com-
pound was isolated from the mother liquor of 6 by silica gel
chromatography (6% yield), and the spectral data was identical
with those of a synthetic sample.10 Mp 273-275 °C (MeOH)
[lit.10 mp 268-270 °C]. TLC (CH2Cl2/EtOAc (10/1)) Rf 0.85.
1H NMR: δ 0.97 (s, 3), 0.98 (s, 6), 1.04 (s, 3), 1.10 (s, 3), 1.38
(s, 3), 1.10 (s, 3), 1.24 (s, 3), 1.2-2.0 (m, 20), 2.51 (m, 2), 3.95
(t, 1, J ) 2.6), 4.96 (d, 2, J ) 13.0), 5.07 (d, 2, J ) 13.0). 13C
NMR: δ 16.7, 18.2, 18.9, 19.8, 20.9, 22.2, 23.8, 26.8, 27.1, 28.4,
31.7, 33.1, 33.8, 34.0, 36.3, 38.2, 39.6, 42.7, 44.4, 44.5, 45.8,
47.3, 51.1, 54.6, 71.6, 75.6, 88.3, 179.1, 217.2. [R]23D +54.6° (c
1.007, CHCl3). HR-LSIMS m/ z 532.3276 [M + H]+ (calcd for
C30H46NO7, 532.3272).
Nitr im in e 11. A solution of 8 (120 mg, 0.24 mmol) in
dioxane (3 mL) and AcOH (8 mL) was treated with a 5%
aqueous solution of NaNO2 (6 mL) at room temperature for
24 h. The precipitate was collected, washed with water, and
recrystallized from CHCl3-MeOH to give nitrimine 11 (80 mg,
63%). Mp > 300 °C. IR (KBr): 3396, 2962, 1758, 1704, 1572,

Partial Synthesis of Myriceric Acid A
1299, 970 cm-1 1H NMR (CDCl3+CD3OD): δ 0.89 (s, 3), 0.94
J . Org. Chem., Vol. 62, No. 4, 1997 965
.
3.94 (br d, 1, J ) 8.6), 9.99 (s, 1). 13C NMR: δ 17.1, 18.2, 18.9,
20.79, 20.84, 21,3, 24.4, 26.8, 27.0, 28.2, 31.6, 33.0, 33.6, 33.7,
35.5, 36.6, 37.7, 39.3, 43.2, 44.6, 44.2, 47.1, 49.8, 54.3, 58.3,
75.0, 87.1, 178.9, 210.1, 217.5. [R]23.5D +60.5° (c 1.003, CHCl3).
Anal. Calcd for C30H46O4: C, 74.34; H, 9.15. Found: C, 74.18;
H, 9.14. LSIMS m/ z 485 [M + H]+.
Eth ylen e Keta l 16. A suspension of hydroxy aldehyde 15
(267 g, 0.552 mol), toluene (2.67 L), ethylene glycol (308 mL),
and PPTS (6.9 g, 28 mmol) was refluxed for 4 h with azeotropic
removal of water with a Dean-Stark apparatus filled with
molecular sieves. The resulting mixture was cooled and
(s, 3), 0.98 (s, 3), 1.04 (s, 3), 1.08 (s, 3), 1.30 (s, 3), 1.2-2.6 (m,
24), 3.98 (br s, 1), 9.21 (s, 1). 13C NMR (CDCl3+CD3OD): δ
17.6, 18.3, 19.3, 20.3, 20.7, 20.9, 24.3, 27.2, 27.3, 28.3, 31.5,
32.9, 33.9, 36.3, 36.7, 37.1, 39.3, 44.1, 45.1, 46.8, 47.4, 50.8,
51.3, 54.6, 74.7, 87.6, 179.2, 179.9, 219.2. Anal. Calcd for
C30H44N2O6: C, 68.16; H, 8.39; N, 5.30. Found: C, 67.79; H,
8.33; N, 5.08. HR-LSIMS m/ z 551.3090 [M + Na]+ (calcd for
C30H44N2O6Na, 551.3094).
Cyclic Eth er 12. A mixture of 6 (106 mg, 0.226 mmol),
Pb(OAc)4 (416 mg, 0.939 mmol), I2 (70.6 mg, 0.278 mmol), and
CaCO3 (161 mg, 1.61 mmol) in CHCl3 (10 mL) was sonicated
at 25-35 °C for 2 h. The mixture was poured into saturated
NaHCO3 (15 mL). The aqueous phase was extracted with
CHCl3 (3 × 15 mL) and the combined fractions were dried and
concentrated under reduced pressure. The residue was puri-
fied by silica gel chromatography (toluene/CHCl3/EtOAc (20/
6/3)) to give cyclic ether 12 (63 mg, 60%). Recrystallization
from CHCl3/EtOAc gave an analytically pure sample: mp >
washed with H2
O (560 mL), and the aqueous layer was
extracted with toluene-EtOAc (560 mL-280 mL). The or-
ganic layers were combined and concentrated to give crude
16 (320.3 g). A pure sample was obtained by silica gel
chromatography. TLC (CH2Cl2/EtOAc (8/1)) Rf 0.74. HPLC
(MeCN/H2
O/AcOH (65/35/0.1) tR 13.3 min. IR (CHCl3): 3020,
3017, 2956, 1770, 1730, 1703 cm-1
.
1H NMR: δ 0.79 (s, 3),
0.89 (s, 3), 0.90 (s, 3), 0.94 (s, 6), 1.21 (s, 3), 1.1-2.4 (m, 23),
3.21 (m, 1), 3.85-3.98 (m, 5), 10.02 (s, 1). 13C NMR: δ 17.0,
17.7, 18.5, 20.0, 20.9, 21,1, 22.8, 24.5, 26.9, 26.9, 27.9, 31.5,
33.1, 33.7, 36.3, 36.9, 37.1, 37.5, 42.2, 43.4, 44.7, 45.9, 49.9,
300 °C. IR (KBr): 3435, 2945, 1770, 1708, 976 cm-1
.
1H
NMR: δ 0.95 (s, 3), 1.00 (s, 3), 1.01 (s, 3), 1.05 (s, 3), 1.09 (s,
3), 1.11 (s, 3), 1.2-1.9 (m, 19), 1.9-2.1 (m, 1), 2.16 (dd, 1, J )
13.4, 3.2), 2.4-2.6 (m, 2), 3.64 (d, 1, J ) 9.3), 4.06 (d, 1, J )
4.5), 4.19 (d, 1, J ) 9.3). 13C NMR: δ 16.4, 18.2, 18.8, 19.7,
20.7, 22.1, 24.1, 25.6, 26.1, 26.3, 31.0, 33.1, 33.3, 33.8, 33.9,
36.4, 37.3, 38.9, 42.4, 42.5, 46.4, 47.3, 48.3, 49.1, 55.2, 74.5,
77.6, 90.5, 179.9, 217.2. [R]22D -15.7° (c 1.009, CHCl3). Anal.
Calcd for C30H44O4: C, 76.88; H, 9.46. Found: C, 76.85; H,
9.44. LSIMS m/ z 469 [M + H]+.
53.2, 58.4, 64.9, 75.4, 87.2, 112.9, 179.2, 209.8 . [R]23.5
+3.5°
D
(c 1.011, CHCl3). LSIMS m/ z 529 [M + H]+.
Ald eh yd e Aceta te 17. The crude 16 (320 g, 0.552 mol)
was dissolved in CH2Cl2 (1.17 L), and to the solution were
added pyridine (156 mL), acetic anhydride (130 mL, 1.38 mol),
and DMAP (6.74 g, 55 mmol). After stirring the mixture at
room temperature for 5 h, 2 N HCl (1.93 L) was added under
ice cooling. The organic layer was separated and washed
successively with H2O (1.68 L), 10% NaHCO3 (1.68 L), and
H2O (1.68 L), and the aqueous layers were extracted with CH2-
Cl2 (0.56 L). Combined organic layers were concentrated, and
the residue was triturated with hexane (1.12 L) to give 17 as
a white powder (303.7 g, 96%): mp 225-227 °C. TLC (hexane/
EtOAc (1/1)) Rf 0.73. HPLC (MeCN/H2O/AcOH (75/25/0.1) tR
11.8 min. IR (CHCl3): 3021, 2957, 1776, 1745, 1708, 1233
Im in e 13. To a solution of oxime 8 (450 g, 0.90 mol) in
dioxane (4.5 L) and AcOH (450 mL) was added 20% aqueous
TiCl3 (2.25 L) under ice cooling with the temperature main-
tained at 26 °C. Stirring was continued for 4 h, and the
resulting solution was added to a mixture of EtOAc (13.5 L),
Na2CO3 (1.66 kg, 17.4 mol), and H2O (13.5 L) over 30 min with
stirring and occasional addition of ice to keep the temperature
below 40 °C. The organic layer was separated and washed
with brine and water. The aqueous layer was extracted with
two portions of EtOAc (10 L). The extracts were combined
and concentrated to give crude imine 13 (480 g). The analyti-
cally pure sample was obtained by crystallization from hexane
(88%) to provide a white powder: mp 263-266 °C dec. TLC
(CH2Cl2/EtOAc (8/1)) Rf 0.23. HPLC (MeCN/H2O/AcOH (65/
35/0.1)) tR 3.77 min. IR (CHCl3): 3017, 2953, 1766, 1699, 1636
cm-1 1H NMR: δ 0.81 (s, 6) 0.90 (s, 3), 0.92 (s, 3), 0.94 (s, 3),
.
1.21 (s, 3), 1.0-2.3 (m, 23), 2.12 (s, 3), 3.86-3.99 (m, 4), 5.27
(t, 1, J ) 2.8), 10.24 (s, 1). 13C NMR: δ 17.0, 17.7, 18.5, 19.0,
20.0, 20,7, 21.5, 22.9, 24.5, 24.8, 26.8, 31.4, 33.1, 33.4, 36.2,
36.4, 37.1, 37.2, 42.2, 42.3, 44.6, 48.1, 49.2, 53.4, 58.7, 64.9,
64.9, 76.8, 85.3, 112.8, 169.0, 178.3, 206.8 . [R]23.5 +4.5° (c
D
1.008, CHCl3). Anal. Calcd for C34H50O7: C, 71.55; H, 8.83.
Found: C, 71.21; H, 8.77. LSIMS m/ z 571 [M + H]+.
cm-1 1H NMR: δ 0.89 (s, 3), 0.92 (s, 3), 0.98 (s, 3), 1.02 (s, 3),
.
1.05 (s, 3), 1.1-1.7 (m, 16), 1.30 (s, 3), 1.8-2.3 (m, 6), 2.44-
2.52 (m, 2), 3.76 (d, 1, J ) 10.3), 6.99 (d, 1, J ) 10.3), 8.11 (d,
1, J ) 14.8). 13C NMR: δ 16.6, 18.3, 18.9, 20.9, 21.2, 24,0,
25.7, 26.9, 27.0, 28.4, 31.6, 33.2, 33.8, 33.9, 35.0, 36.3, 39.4,
40.6, 43.1, 43.4, 44.7, 47.1, 50.0, 53.2, 54.6, 74.5, 89.0, 179.1,
Red u ctive Olefin Regen er a tion a n d Myr icer on e Keta l
18. Lithium metal (11.1 g, 1.60 mol) was dissolved in liquid
NH3 (1.3 L), and to the solution was added a solution of 17
(152 g, 0.266 mol) in THF (1.3 L) over 1 h. After stirring for
45 min, EtOH (152 mL) was added, and the resulting solution
was evaporated with gentle heating. 2 N HCl (2 L) was then
added while keeping the temperature around 25 °C with
occasional addition of ice, and 6 N HCl (200 mL) was added to
bring the pH to 3. The mixture was extracted with CH2Cl2
(1.6 L) and H2O (1.6 L), and the organic layer was washed
with H2O. The aqueous layer was extracted with CH2Cl2 (0.8
L), and the organic layers were combined and concentrated to
give crude myricerone ketal 18 (187 g). Analytically pure 18
was obtained by chromatography (hexane-EtOAc, 90% yield)
and subsequent crystallization from MeOH, mp 218-220 °C.
TLC (CH2Cl2/EtOAc (8/1)) Rf 0.33. HPLC (MeCN/H2O/AcOH
(80/20/0.1)) tR 5.2 min. IR (CHCl3): 3016, 2952, 2882, 1695,
182.6, 217.7. [R]23.5 +65.6° (c 1.008, CHCl3). Anal. Calcd
D
for C30H45NO4: C, 74.50; H, 9.38; N, 2.90. Found: C, 74.33;
H, 9.43; N, 2.90. LSIMS m/ z 484 [M + H]+.
12r-Hydr oxy-3,27-dioxoolean an o-28,13-lacton e 15. The
crude imine 13 (480 g) obtained above was dissolved in dioxane
(4.36 L) and AcOH (436 mL) at 40 °C. To the solution was
added an aqueous solution of NaNO2 (186 g in 654 mL of H2O)
at 23 °C, and the resulting mixture was stirred for 1 h. HPLC
of the reaction mixture showed the ratio of hemiacetal acetate
14 and 15 to be 1 to 2 (HPLC (MeCN/H2O/AcOH (65/35/0.1) tR
14 (12 min), 15 (9.0 min)). MeOH (2.83 L) and 2 N NaOH
(4.0 L) were added to the resulting mixture maintaining the
temperature between 14-26 °C, and the mixture was stirred
for 2.5 h. The mixture was neutralized with 2 N HCl (1.0 L)
and poured into a mixture of brine (8 L) and EtOAc (8 L). The
organic layer was washed with brine, and the aqueous layer
was extracted with EtOAc (6.5 L). The organic layers were
combined, dried, and concentrated to 750 g. The residue was
dissolved in EtOAc (2.6 L) and concentrated to 860 g. The
resulting thick slurry was kept at 0 °C overnight, and the
colorless crystalline powder was collected by filtration and
washed with cold EtOAc (0.4 L) to give hydroxy aldehyde 15
(337 g, 77%). Mp 296-300 °C. TLC (CH2Cl2/EtOAc (8/1)) Rf
1210 cm-1 1H NMR: δ 0.70 (s, 3), 0.83 (s, 3), 0.90 (s, 3), 0.91
.
(s, 3), 0.92 (s, 3), 0.96 (s, 3) , 1.1-2.0 (m, 24), 2.92 (dd, 1, J )
13.0, 4.0), 3.16 (d, 1, J ) 11.8), 3.78 (d, 1, J ) 11.8) 3.93 (br s,
4), 5.83 (br s, 1). 13C NMR: δ 15.7, 18.3, 18.6, 20.1, 22.4, 23.0,
23.9, 24.2, 24.5, 26.6, 30.8, 32.3, 33.0, 33.5, 36.5, 37.0, 39.8,
40.3, 42.0, 44.9, 46.1, 47.5, 48.0, 52.9, 62.9, 64.8, 113.2, 129.5,
137.9, 184.0. [R]23.5 +42.4° (c 1.003, CHCl3). Anal. Calcd
D
for C32H50O5: C, 74.67; H, 9.79. Found: C, 74.52; H, 9.82.
LSIMS m/ z 515 [M + H]+.
Myr icer on e (27-h yd r oxy-3-oxoolea n -12-en -28-oic Acid )
(3). To a solution of crude 18 (187 g, obtained from 0.266 mol
of 17) in THF (685 mL) was added 2 N HCl (137 mL), and the
resulting solution was refluxed for 75 min. After cooling to
room temperature, the mixture was extracted with CH2Cl2/
0.60. IR (CHCl3): 3018, 2957, 1771, 1703 cm-1 1H NMR: δ
.
0.90 (s, 3), 0.94 (s, 3), 0.98 (s, 3), 1.02 (s, 3), 1.06 (s, 3), 1.26 (s,
3), 1.1-2.3 (m, 21), 2.46-2.53 (m, 2), 3.55 (br d, 1, J ) 8.6),

966 J . Org. Chem., Vol. 62, No. 4, 1997
Konoike et al.
H2O (1.6 L/3.2 L). The organic layer was washed with H2O
(3.2 L), and the aqueous layer was extracted with CH2Cl2 (1.6
L). The combined organic extracts were concentrated, and
triturated from CH2Cl2/hexane (0.2 L/1.26 L) to give 3 as a
hygroscopic white powder (125 g, 99%). The spectral data
(NMR, IR, [R]D) of the synthetic sample were identical to those
of an authentic sample1 obtained by alkaline hydrolysis of
natural myriceric acid A (1). 3: mp 211-213 °C (MeOH). TLC
(CH2Cl2/EtOAc (8/1)) Rf 0.74. HPLC (MeCN/H2O/AcOH (80/
(m, 1), 2.93 (d, 2, J ) 21.7), 4.05-4.36 (m, 6), 5.59 (br s, 1).
13C NMR: δ 15.3, 16.4, 16.5, 18.0, 19.6, 21.4, 22.8, 23.5, 23.7,
26.6, 30.7, 32.4, 32.8, 33.0, 33.6, 33.7 34.0, 35.4, 37.0, 39.0,
39.9, 40.8, 45.0, 46.3, 46.4 (d, J ) 151), 47.8, 55.1, 62.7 (d, J )
6.6), 62.8 (d, J ) 6.6), 66.7, 127.3, 137.3, 165.6, 183.4, 217.3.
[R]23D +85.6° (c 1.005, CHCl3). Anal. Calcd for C36H57O8P: C,
66.64; H, 8.85, P, 4.77. Found: C, 66.33; H, 8.83, P, 4.92. HR-
LSIMS m/ z 649.3863 [M + H]+ (calcd for C36H57O8P, 649.3866).
3,4-Bis[(d ip h en ylm eth yl)oxy]ben za ld eh yd e 21. A mix-
ture of 3,4-dihydroxybenzaldehyde (1.38 g, 10 mmol), bromo-
diphenylmethane (5.43 g, 22 mmol), pulverized K2CO3 (3.45
g, 25 mmol) in DMF (20 mL) was heated at 80 °C for 5 h.
Additional portions of bromodiphenylmethane (5.43 g, 22
mmol), and pulverized K2CO3 (3.45 g, 25 mmol) were added,
and the mixture was heated at 80 °C for 3 h. The mixture
was extracted with EtOAc, and the organic layer was washed
with 5% HCl and aqueous NaHCO3. The extracts were
concentrated and purified by chromatography (toluene/EtOAc
(19/1)) to give 3,4-bis[(diphenylmethyl)oxy]benzaldehyde 21
(10.8 g, 23%) as a colorless oil. TLC (hexane/EtOAc ) 2/1) Rf
0.35. IR (KBr): 3029, 1683, 1597, 1578, 1503, 1454, 1435, 1264
20/0.1)) tR 3.3 min. IR (CHCl3): 3010, 2945, 2867, 1697 cm-1
.
1H NMR: δ 0.79 (s, 3), 0.94 (s, 3) 0.98 (s, 3), 1.03 (s, 6), 1.11
(s, 3), 1.1-2.1 (m, 22), 2.3-2.6 (m, 2), 2.97 (br d, 1, J ) 12.8),
3.26 (d, 1, J ) 11.8), 3.81 (d, 1, J ) 12.2), 5.89 (br s, 1). 13C
NMR: δ 15.5, 18.3, 19.5, 21.4, 22.4, 23,8, 24.1, 24.4, 26.5, 36.8,
32.0, 32.2, 33.0, 33.5, 34.0, 36.8, 38.7, 39.7, 40.4, 44.9, 46.1,
47.3, 47.6, 54.7, 63.0, 129.3, 137.8, 183.7, 217.6. [R]23.5
D
+101.0° (c 1.003, CHCl3). Anal. Calcd for C30H46O4‚0.2H2O:
C, 75.97; H, 9.88. Found: C, 76.23; H, 10.18. HR-LSIMS m/ z
493.3296 [M + Na]+ (calcd for C30H46O4Na, 493.3294).
Dim er iza tion P r od u ct 20. Lithium metal (0.14 g, 20
mmol) was dissolved in liquid NH3 (10 mL), and to the solution
was added a solution of 17 (2.28 g, 0.266 mmol) in THF (23
mL) over 30 min. After stirring for 2.5 h, EtOH (3 mL) was
added, and the resulting solution was evaporated with gentle
heating. The remaining mixture was extracted as described
above, and crude myricerone ketal 18 containing the two
byproducts was obtained (1.92 g). The residue was deketalized
as described above, and the remaining mixture was separated
by silica gel chromatography (CH2Cl2-EtOAc) to give myricero-
ne 3 (0.96 g, 46%), aldehyde 19 (0.1 g, 5%), and dimer 20 (0.4
g, 21%). HPLC: tR (min), myricerone 4 (4.5), aldehyde 19 (5.7),
dimer 20 (17.5). Aldehyde 19 was identical with an authentic
sample prepared from PCC oxidation of 3. 20: mp 168-171
°C. TLC (hexane/EtOAc (2/1)) Rf 0.15. IR (CHCl3): 3489,
cm-1 1H NMR: δ 6.35 (s, 2), 6.92 (d, 1, J ) 8.4), 7.1-7.5 (m,
.
22), 9.67 (s, 1). 13C NMR: δ 82.9, 83.1, 115.6, 115.8, 126.6,
126.9, 127.1, 128.1, 128.2, 128.9, 129.0, 130.5, 141.1, 141.5,
149.0, 154.4, 191.1. Anal. Calcd for C33H26O3: C, 84.23; H,
5.57. Found: C, 84.42; H, 5.75.
tr a n s-27-O-[3,4-b is[(d ip h en ym et h yl)oxy]cin n a m oyl]-
m yr icer on e (22). A mixture of 2 (390 mg, 0.6 mmol), 3,4-
bis[(diphenylmethyl)oxy]benzaldehyde (21) (338 mg, 0.72 mmol),
DBU (0.402 mL, 2.7 mmol), and LiCl (114 mg, 2.7 mmol) in
DMF (4 mL) was stirred at room temperature for 5 h. The
mixture was extracted with EtOAc, and the organic layer was
washed with 5% HCl and aqueous NaHCO3. The extracts
were concentrated to give crude 22 as a white foam (648 mg).
An analytically pure sample was obtained by chromatography
(hexane/EtOAc (2/1)) in 95% yield. Mp 153-159 °C (MeOH).
1700, 1460, 1378 cm-1 1H NMR and 13C NMR spectrum were
.
determined and assigned at 600 and 150 MHz, respectively,
by Varian UNITY 600 instrument. Long range correlations
were observed between C-27 and 27′-H in the HMBC (hetero-
nuclear multiple bond connectivity) spectrum. 1H NMR
(CDCl3-CD3OD): δ 0.80 (s, 6), 0.87 (s, 6), 0.96 (s, 6), 1.01 (s,
6), 1.04 (s, 6), 1.05 (s, 6), 1.13 (dd, 2, J ) 14.0, 4.3), 1.27 (m,
2), 1.29 (m, 2), 1.32 (m, 2), 1.33 (m, 2), 1.37 (m, 2), 1.42 (m, 2),
1.43 (m, 2), 1.52 (m, 2), 1.56 (m, 2), 1.69 (d, 2, J ) 10.9), 1.69
(m, 2), 1.80 (m, 2), 1.85 (m, 2), 1.91 (m, 2), 1.93 (m, 2), 2.00
(m, 2), 2.03 (m, 2), 2.10 (ddd, 2, J ) 18.8, 7.1, 3.3), 2.31 (ddd,
2, J ) 15.8, 5.6, 2.8), 2.37 (dd, 2, J ) 10.5, 7.2), 2.59 (ddd, 2,
J ) 15.8, 12.3, 6.9), 3.00 (dd, 2, J ) 13.9, 4.3), 3.4-3.6 (br, 4),
4.02 (s, 2), 5.84 (t, 2, J ) 3.3). 13C NMR (CDCl3-CD3OD): δ
15.3, 19.8, 20.3, 21.8, 23.0, 23.4, 23.6, 24.8, 25.9, 30.7, 31.3,
32.5, 33.3, 33.7, 34.5, 37.4, 39.1, 41.2, 42.1, 45.0, 45.5, 46.6,
47.7, 52.7, 53.0, 69.3, 130.3, 140.0, 180.6, 219.4. LSIMS m/ z
939 [M + H]+. HR-LSIMS m/ z 961.6521 [M + Na]+ (calcd
for C60H90O8Na, 961.6528). Both the NMR spectrum and the
HRMS supported the dimeric structure of 20.
TLC (hexane/EtOAc (2/1)). Rf 0.55. [R]23 +88.3° (c 1.012,
D
CHCl3). IR (KBr): 3432, 2864, 1701, 1631, 1596, 1504, 1454
cm-1 1H NMR: δ 0.83 (s, 6), 0.93 (s, 3), 1.03 (s, 3), 1.04 (s, 3),
.
1.07 (s, 3), 1.05-2.05 (m, 20), 2.1-2.6 (m, 2), 2.8-3.0 (m, 1),
4.10 (d, 1, J ) 13.0), 4.32 (d, 1, J ) 13.0), 5.62 (br s, 1), 6.00
(d, 1, J ) 16.0), 6.26 (s, 1), 6.30 (s, 1), 6.84 (d, 1, J ) 8.6),
6.9-7.0 (m, 2), 7.2-7.6 (m, 22). 13C NMR: δ 14.1, 15.2, 18.1,
19.5, 21.4, 22.6, 22.6, 23.6, 24.0, 26.6, 30.5, 31.6, 32.3, 32.4,
32.9, 33.6, 33.9, 36.8, 38.8, 39.9, 40.8, 44.5, 45.2, 46.3, 47.2,
47.7, 54.9, 65.3, 82.8, 83.4, 116.1, 116.4, 116.7, 122.6, 126.7,
126.8, 127.7, 127.8, 128.5, 137.3, 141.1, 141.3, 144.4, 148.6,
150.9, 166.7, 184.3, 217.3. Anal. Calcd for C65H72O7: C, 80.88;
H, 7.52. Found: C, 80.51; H, 7.81. HR-LSIMS m/ z 987.5180
[M + Na]+ (calcd for C65H72O7Na, 987.5172).
Myr icer ic Acid A 1. Trifluoroacetic acid (0.7 mL) was
added to the solution of crude 22 (341 mg, 0.316 mmol) in
anisole (2.0 mL) at 0 °C, and the resulting mixture was stirred
at room temperature for 1.5 h. The mixture was condensed
under reduced pressure and purified by silica gel chromatog-
raphy (toluene/EtOAc (2/1)) to give 1 (160 mg, 80% from 2) as
a white powder. The spectral data (NMR, IR, [R]D) of the
synthetic sample were identical to those of the natural
product.1
27-O-(Diet h ylp h osp h on oa cet yl)m yr icer on e (2). To a
solution of diethylphosphonoacetic acid (230 g, 1.17 mol) in
CH2Cl2 (2.2 L) was added carbonyldiimidazole (190 g, 1.17 mol)
portionwise over 10 min, and subsequently myricerone 3 (220
g, 0.468 mol). After the mixture was stirred for 6 h at room
temperature, 1 N HCl (2.2 L) was added to the mixture, and
the organic layer was separated and washed with H2O (2.2
L). The aqueous layer was extracted with CH2Cl2 (0.5 L), and
the organic extracts were combined and concentrated to give
crude 2 as a white foam (318 g). The foam was dissolved in
EtOAc (340 mL) under reflux, and white crystals precipitated
on cooling. The crystals were collected by filtration and
washed with cold EtOAc (0.25 L) to give 2 which contained
7% of EtOAc (288 g, 84%). An analytically pure sample was
obtained by recrystallization from MeCN: mp 109-112 °C.
TLC (CH2Cl2/EtOAc (2/1)) Rf 0.21. HPLC (MeCN/H2O/AcOH
(65/35/0.1) tR 5.3 min. IR (CHCl3): 3027, 1730, 1697, 1261
Ack n ow led gm en t. The authors are grateful to
Messrs. K. Oda, I. Yamada, M. Uenaka, and Y. Sugata
for their contribution to the improvement of the large-
scale preparation.
1
Su p p or tin g In for m a tion Ava ila ble: Copies of H NMR
spectra of compounds 9, 16, 19, and 20 which lack elemental
analyses (4 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
cm-1
.
1H NMR: δ 0.79 (s, 3), 0.89 (s, 3), 0.93 (s, 3), 1.02 (s, 3),
1.08 (s, 3), 1.11 (s, 3), 1.1-2.1 (m, 27), 2.3-2.6 (m, 2), 2.8-3.0
J O9615864