Stereoselective Construction of Copaborneol and Longiborneol Frameworks by Intramolecular Double Michael Reaction

Article abstract of DOI:10.1021/jo960698s

Stetreoselective synthesis of tricyclo<5.3.0.0^3,8>decane 22 and tricyclo<6.3.0.O^3,9>undecane 26 the basic skeleton of copaborneol and longiborneol, were achieved by the intramolecular double Michael reactions of 2-cyclopenten-1-ones 15-17.The substrates were prepared starting with tricyclo<5.2.1.0^2,6>deca-4,8-dien-3-one (6).The intramolecular double Michael reactions were carried out under three different conditions: TMSCl-Et3N-ZnCl2.TMSI-(TMS)2NH, and Bu2BOTf-(TMS)2NH.The framework 26 of longiborneol was constructed in good yield using the latter two reagent systems.

Full text of DOI:10.1021/jo960698s

6416
J . Org. Chem. 1996, 61, 6416-6421
Ster eoselective Con str u ction of Cop a bor n eol a n d Lon gibor n eol
F r a m ew or k s by In tr a m olecu la r Dou ble Mich a el Rea ction
Masataka Ihara, Kei Makita, Yuki Fujiwara, Yuji Tokunaga, and Keiichiro Fukumoto*
Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-77, J apan
Received April 17, 1996X
Stereoselective syntheses of tricyclo[5.3.0.03,8]decane 22 and tricyclo[6.3.0.03,9]undecane 26, the basic
skeletons of copaborneol and longiborneol, were achieved by the intramolecular double Michael
reactions of 2-cyclopenten-1-ones 15-17. The substrates were prepared starting with tricyclo-
[5.2.1.02,6]deca-4,8-dien-3-one (6). The intramolecular double Michael reactions were carried out
under three different conditions: TMSCl-Et3N-ZnCl2, TMSI-(TMS)2NH, and Bu2BOTf-
(TMS)2NH. The framework 26 of longiborneol was constructed in good yields using the latter two
reagent systems.
In tr od u ction
time and were extremely useful for the synthesis of the
tricyclo[6.3.0.03,9]undecane ring system. Several results
supporting the stepwise mechanism have been obtained
during this study.
There are many sesquiterpenes characterized by the
presence of a bicyclo[2.2.1]heptane system with an ad-
ditional three or four carbon bridge, e.g., (+)-copaborneol
(the antipode of 1)1 or (+)-logiborneol (2).2 Although most
synthetic approaches to these natural products are
composed of the stepwise constructions of three rings,3
the routes utilizing the intramolecular Diels-Alder reac-
tion (IDA) seem to be attractive since two rings are
assembled in one step. Fallis achieved the short syn-
thesis of (+)-longifolene using this strategy.4 Snowden
reported the IDA approach to the tricyclo[4.3.0.03,7]-
nonane, which is convertible to (()-sativene.5 The in-
tramolecular double Michael reaction (IDM) is similar
to the IDA and has several advantages over the IDA:
high stereoselectivity, complete regioselectivity, milder
reaction conditions, and so forth.6 As an extension of the
IDM strategy, the construction of tricyclo[5.3.0.03,8]-
decane and tricyclo[6.3.0.03,9]undecane systems 4 was
investigated starting with 2-cyclopenten-1-ones 3. The
desired transformation was performed under three condi-
tions using (A) TMSCl-Et3N-ZnCl2,5,7 (B) TMSI-(TMS)2-
NH,8,9 and (C) Bu2BOTf-(TMS)2NH.10 The latter two
conditions B and C were applied to the IDM for the first
Resu lts a n d Discu ssion
P r ep a r a tion of Su bstr a tes. It is expected that
2-cyclopenten-1-ones 3 possessing an R,â-unsaturated
ester side chain could be readily derived from 5, which
would be prepared by the introduction of two appropriate
alkyl groups to the enone 611 (Scheme 1).
Sch em e 1
X Abstract published in Advance ACS Abstracts, August 15, 1996.
(1) (a) Kolbe, M.; Westfelt, L. Acta Chem. Scand. 1967, 21, 585-
587. (b) Kolbe-Haugwitz, M; Westfelt, L. Acta Chem. Scand. 1970, 24,
1623-1630. (c) Piers, E.; Britton, R. W.; Geraghty, M. B.; Keziere, R.
J .; Smillie, R. D. Can. J . Chem. 1975, 53, 2827-2837.
(2) (a) Naffa, P.; Ourisson, G. Bull. Soc. Chim. Fr. 1954, 5, 1410-
1415. (b) Akiyoshi, S.; Erdtman, H.; Kubota, T. Tetrahedron 1960, 9,
237-239. (c) Welch, S. C.; Walters, R. L. J . Org. Chem. 1974, 39, 2665-
2673. (d) Kuo, D. L.; Money, T. J . Chem. Soc., Chem. Commun. 1986,
1691-1692.
(3) (a) Heathcock, C. H. In The Total Synthesis of Natural Products;
ApSimon, J ., Ed.; J ohn Wiley & Sons: New York, 1973; Vol. 2, pp 197-
558. (b) Heathcock, C. H.; Graham, S. L.; Pirrung, M. C.; Plavac, F.;
White, C. T. In The Total Synthesis of Natural Products; ApSimon, J .,
Ed.; J ohn Wiley & Sons: New York, 1983; Vol. 5, pp 1-550.
(4) (a) Lei, B.; Fallis, A. G. J . Am. Chem. Soc. 1990, 112, 4609-
4610. (b) Lei, B.; Fallis, A. G. J . Org. Chem. 1993, 58, 2186-2195.
(5) (a) Snowden, R. L. Tetrahedron Lett. 1981, 22, 97-100. (b)
Snowden, R. L. Tetrahedron 1986, 42, 3277-3290.
(6) Ihara, M.; Fukumoto, K. Angew. Chem., Int. Ed. Engl. 1993, 32,
1010-1022.
According to the above considerations, the conjugate
addition of the Grignard reagents of four carbon units to
611 was first examined under various conditions but poor
results were obtained. The introduction of four carbon
(7) Danishefsky, S.; Kitahara, T. J . Am. Chem. Soc. 1974, 96, 7807-
7808.
(8) Miller, R. D.; McKean, D. R. Synthesis 1979, 730-732.
(9) (a) Ihara, M.; Taniguchi, T.; Makita, K.; Takano, M.; Ohnishi,
M.; Taniguchi, N.; Fukumoto, K.; Kabuto, C. J . Am. Chem. Soc. 1993,
115, 8107-8115. (b) Ihara, M.; Taniguchi, T.; Tokunaga, Y.; Fukumoto,
K. J . Org. Chem. 1994, 59, 8092-8100.
(10) Ihara, M.; Taniguchi, T.; Yamada, M.; Tokunaga, Y.; Fukumoto,
K. Tetrahedron Lett. 1995, 34, 8071-8074.
(11) (a) Woodward, R. B.; Katz, T. J . Tetrahedron 1959, 5, 70-89.
(b) Takano, S.; Moriya, M.; Tanaka, K.; Ogasawara, K. Synthesis 1994,
687-688.
S0022-3263(96)00698-6 CCC: $12.00 © 1996 American Chemical Society

Construction of Copaborneol and Longiborneol Frameworks
J . Org. Chem., Vol. 61, No. 18, 1996 6417
Sch em e 2
Sch em e 3
deprotection (94%), followed by oxidation and the sub-
sequent Wittig reaction, produced 16 in 68% overall yield
from 14. When the final reaction was carried out using
Still’s reagent14 in the presence of potassium hexameth-
yldisilazide (KHMDS) and 18-crown-6, the (Z)-isomer 17
was obtained in 55% overall yield from 14 together with
the (E)-isomer 16 (3% yield). Both isomers 16 and 17
were easily separated by column chromatography on
silica gel.
In tr a m olecu la r Dou ble Mich a el Rea ction (IDM).
The IDM has so far been carried out under three different
conditions: lithium hexamethyldisilazide (LHMDS), TB-
DMSOTf-Et3N, and TMSCl-Et3N-ZnCl2.6 The reaction
of 15 with LHMDS gave an intractable mixture, while
bicyclic 18 was formed in 99% yield as a 1:1.8 diastere-
oisomeric mixture by treatment with TBDMSOTf in the
presence of Et3N in CH2Cl2. Since the product was
converted into enone 20 in two steps (Scheme 3), the
tricyclic structure 21, formed by the intramolecular
Michael-aldol reaction, was excluded.
units retaining the olefin function was achieved by the
application of Kozikowski’s method.12 Namely, the 1,4-
addition of triphenylphosphine to 6 in the presence of
tert-butyldimethylsilyl trifluoromethanesulfonate (TB-
DMSOTf), followed by treatment with butyllithium,
produced an ylide, which was subjected to the Wittig
reaction. The resulting silyl enol ether was treated with
tetrabutylammonium fluoride to afford 7 in 78% overall
yield from 6 (Scheme 2). Introduction of a methyl group
to 7 was also difficult, and the conversion was carried
out in a reasonable yield with Gilman reagent in the
presence of boron trifluoride etherate.13 When the hy-
droxyl group was protected with a tetrahydropyranyl
group, unsatisfactory results were observed due to the
deprotection during the reaction. Therefore, the protec-
tion of the hydroxyl group with the tert-butyldiphenylsilyl
(TBDPS) group was crucial.
The retro Diels-Alder reaction of 9, obtained in 72%
yield, was carried out in refluxing o-dichlorobenzene
(ODB), and provided 11 in 97% yield. After deprotection
of the TBDPS group, the resulting 13, produced in 88%
yield, was oxidized with pyridinium chlorochromate
(PCC) in the presence of 4 Å molecular sieves and then
subjected to the Wittig reaction utilizing a stable ylide
to give 15 in 68% overall yield from 13.
Upon treatment of 15 with TMSCl, Et3N, and ZnCl2
in toluene in a sealed tube at 180 °C for 72 h, the desired
tricyclic compounds 22 and 23 were produced in 31% and
9% yields, respectively (Scheme 4 and Table 1, entry 1).
In the IR spectra (CHCl3) of products, absorptions due
to carbonyl groups were observed at 1730 and 1740 cm-1
1
while the H NMR spectra showed no olefinic resonance.
The long-range coupling (J ) 2.2 Hz) due to the W-
configuration was observed between hydrogens neighbor-
ing on the ester group (3.05 ppm) and the keto carbonyl
1
group (2.32 ppm) in the H NMR spectrum of the major
isomer 22; the observations supported the stereostruc-
ture.
The IDM was further performed under two other
reaction conditions, which had been useful for the in-
tramolecular Michael-aldol reaction.9,10 Namely, the
tricyclic compound 22 was obtained in 10% yield as a
single isomer upon treatment of 15 with TMSI in the
presence of (TMS)NH8,9 in ClCH2CH2Cl at ambient
temperature for 1 h. At the same time, bicyclic products
24 and 25 were produced, respectively, in 37% yield as a
single isomer and in 10% yield as a separable 1:1 mixture
of two stereoisomers, although their stereochemistries
were obscure (Table 1, entry 2). On the other hand,
treatment of 15 with Bu2BOTf in the presence of
According to the same procedure as above, the five-
carbon unit was introduced to 6 to afford 8 in 72% overall
yield, which was methylated giving 10 in 76% yield.
After the retro Diels-Alder reaction (94% yield), the
(12) Kozikowski, A. P.; J ung, S. H. J . Org. Chem. 1986, 51, 3400-
3402.
(13) (a) Smith, A. B., III; J erris, P. J . J . Org. Chem. 1982, 47, 1845-
1855. (b) Yamamoto, Y. Angew. Chem., Int. Ed. Engl. 1986, 25, 947-
959.
(14) Still, W. C.; Gennari, C. Tetrahedron Lett. 1983, 24, 4405-4408.

6418 J . Org. Chem., Vol. 61, No. 18, 1996
Ihara et al.
Sch em e 4
Sch em e 6
It is noteworthy that the (Z)-unsaturated ester (17)
showed considerably different behaviors under the above
three conditions. No tricyclic compound 26 was obtained
by heating 17 with TMSCl, Et3N, and ZnCl2 in toluene
(Table 2, entry 4). The treatment of 17 with TMSI and
(TMS)2NH gave 26 in 67% yield (Table 2, entry 5), while
26 was produced in 7% yield by the reaction with Bu2-
BOTf and (TMS)2NH (Table 2, entry 6). No formation
of the corresponding stereoisomer was observed during
the three reactions.
Ta ble 1. Th e IDM of 15
yield (%) of products
Con sid er a tion of Rea ction Mech a n ism . Although
it is difficult to determine that the above annulations
proceed via a stepwise mechanism or via a concerted
mechanism, the former one seems to be likely based on
the following reasons. The significant amount of stere-
oisomer 23 formed upon the treatment of 15 with
TMSCl-Et3N-ZnCl2 (Table 1, entry 1). Mono Michael
adducts 24 and 25 were obtained by the reaction of 15
with TMSI-(TMS)2NH (Table 1, entry 2). The same
stereoisomer 26 was produced from both the (E)- and (Z)-
unsaturated esters 16 and 17 (Table 2, entries 2, 3, 5,
and 6). However, the (Z)-unsaturated ester 28, prepared
from 27, was readily isomerized to the (E)-unsaturated
ester 29 upon treatment with TMSI and (TMS)2NH in
ClCH2CH2Cl (Scheme 6). Therefore, there is a possibility
of concerted ring formation after the isomerization of the
double bond under the reaction conditions. But no
isomerization was observed when the reaction conditions
using Bu2BOTf-(TMS)2NH were applied to 28. Although
it is obvious that each reaction takes place through
different intermediates, the tandem mechanism is more
reasonable than the concerted one for the annulation
under the stated conditions on the basis of these results.
entry
conditions
22
23
1
TMSCl, Et3N, ZnCl2, 180 °C
TMSI, (TMS)2NH, rt
Bu2BOTf, (TMS)2NH
31
10
28
9
0
0
2a
3
a
Bicyclic compounds 24 and 25 were also obtained in 37% and
10% yields.
Sch em e 5
Ta ble 2. Th e IDM of 16 a n d 17
yield (%)
of 26
entry
substrate
conditions
1
2
3
4
5
6
16
16
16
17
17
17
TMSCl, Et3N, ZnCl2, 180 °C
TMSI, (TMS)2NH, rt
Bu2BOTf, (TMS)2NH, rt
TMSCl, Et3N, ZnCl2, 180 °C
TMSI, (TMS)2NH, rt
29
69
71
0
67
7
Bu2BOTf, (TMS)2NH, rt
Con clu sion s
(TMS)2NH in ClCH2CH2Cl at ambient temperature for
3 h provided 22 in 28% yield. No formations of 23 and
24 were detected by this reaction.
The skeletons of copaborneol (1) and longiborneol (2)
were stereoselectively constructed by the IDM of 2-cy-
clopenten-1-one derivatives 15-17. The reactions were
conducted under three different conditions: TMSCl-
Et3N-ZnCl2, TMSI-(TMS)2NH, and Bu2BOTf-(TMS)2-
NH. It is notable that the seven-membered ring was
effectively built by the IDM, and the reaction was carried
out by TMSI-(TMS)2NH and Bu2BOTf-(TMS)2NH. De-
termination of the reaction mechanism details under each
reaction conditions is an interesting problem for future
studies.
Reactions of 16 with LHMDS and TBDMSOTf-Et3N
gave no tricyclic product. The objective compound 26 was
obtained in 29% yield by heating 16 together with
TMSCl, Et3N, and ZnCl2 in toluene in the sealed tube at
180 °C for 72 h (Scheme 5 and Table 2, entry 1). The
stereochemistry of 26, produced as a single stereoisomer,
was determined by the W-type long range coupling in the
1H NMR spectra. Furthermore, the tricyclic compound
26 was provided in 69% yield upon treatment of 16 with
TMSI in the presence of (TMS)2NH in ClCH2CH2Cl at
ambient temperature for 1 h (Table 2, entry 2) and in
71% yield upon the reaction of 16 with Bu2BOTf in the
presence of (TMS)2NH in ClCH2CH2Cl at ambient tem-
perature for 3 h (Table 2, entry 3).
Exp er im en ta l Section
Gen er a l P r oced u r e. All reactions were carried out under
a positive atmosphere of N2 or Ar unless otherwise indicated.
Solvents were distilled prior to use. THF, Et2O, benzene, and

Construction of Copaborneol and Longiborneol Frameworks
J . Org. Chem., Vol. 61, No. 18, 1996 6419
toluene were distilled from sodium benzophenone while CH2-
Cl2, ClCH2CH2Cl, and ODB were distilled from CaH2 and
stored over 4 Å MS. All new compounds are homogeneous on
TLC, and their purities were verified on the basis of their 300
was converted into 10 (3.5 g, 76%) as a colorless oil: IR (neat)
1
1740 cm-1; H NMR (300 MHz, CDCl3) δ 7.70-7.66 (m, 4H),
7.46-7.34 (m, 6H), 6.20 (dd, 1H, J ) 5.5, 2.7 Hz), 6.03 (dd,
1H, J ) 5.5, 2.7 Hz), 3.67 (t, 2H, J ) 6.5 Hz), 3.19-3.14 (m,
1H), 3.05-2.95 (m, 2H), 2.52 (dd, 1H, J ) 8.4, 3.8 Hz), 1.88
(d, 1H, J ) 18.0 Hz), 1.75 (d, 1H, J ) 18.0 Hz), 1.64-1.12 (m,
10H), 1.06 (s, 9H), 0.95 (s, 3H); HRMS calcd for C28H34O2Si
1
MHz H NMR spectra.
(()-(1S*,2R*,6S*,7R*)-5-[4-(ter t-Bu tyld ip h en ylsiloxy)-
bu tyl]tr icyclo[5.2.1.02,6]d eca -4,8-d ien -3-on e (7). A mixture
of 4-(tert-butyldiphenylsiloxy)butan-1-ol15 (7.0 g, 21.3 mmol),
4 Å molecular sieves (17.6 g), and PDC (8.83 g, 23.5 mmol) in
dry CH2Cl2 (50 mL) was stirred for 2.5 h at rt. After dilution
with Et2O, the mixture was filtered through Celite and then
evaporated. Chromatography on silica gel with AcOEt-
hexane (1:4 v/v) as the eluent gave the corresponding aldehyde
(4.74 g, 68%) as a pale yellowish oil.
To a stirred solution of 6 (1.93 g, 13.2 mmol) and Ph3P (3.81
g, 14.5 mmol) in dry THF (30 mL) at rt was added TBDMSOTf
(3.03 mL, 13.2 mmol). The mixture was then stirred for 30
min at rt. After the addition of 1.56 M BuLi in hexane (8.46
mL, 13.2 mmol) at -78 °C, followed by 30 min of stirring at
-78 °C, to the resulting mixture was added at the same
temperature a solution of the above aldehyde (4.74 g, 14.5
mmol) in dry THF (10 mL). The mixture was stirred for 30
min at rt. After the addition of 1.0 M Bu4NF in THF (15.8
mL, 15.8 mmol) at 0 °C, the mixture was stirred for 30 min at
rt and then diluted with Et2O. The mixture was washed with
brine, dried (Na2SO4), and evaporated to give a residue that
was subjected to column chromatography on silica gel. Elution
with AcOEt-hexane (3:17 v/v) yielded 7 (4.61 g, 78%) as a
colorless oil: IR (neat) 1700 cm-1; 1H NMR (300 MHz, CDCl3)
δ 7.69-7.62 (m, 4H), 7.47-7.34 (m, 6H), 5.98 (dd, 1H, J ) 5.5,
2.9 Hz), 5.73 (dd, 1H, J ) 5.5, 2.9 Hz), 5.68 (s, 1H), 3.69 (t,
2H, J ) 5.7 Hz), 3.26-3.20 (m, 1H), 3.17 (br s, 1H), 2.96 (br s,
1H), 2.83 (t, 1H, J ) 5.1 Hz), 2.28-2.19 (m, 2H), 1.79-1.52
(m, 6H), 1.06 (s, 9H); HRMS calcd for C30H36O2Si (M+)
456.2482, found 456.2516.
t
(M+ - Bu) 429.2248, found 429.2278.
4-[4-(ter t-Bu tyld ip h en ylsiloxy)bu tyl]-4-m eth yl-2-cyclo-
p en ten -1-on e (11). A solution of 9 (1.38 g, 2.92 mmol) in dry
ODB (30 mL) was heated for 48 h under reflux. The reaction
mixture was directly subjected to column chromatography on
silica gel with AcOEt-hexane (3:17 v/v) as the eluent to
provide 11 (1.15 g, 97%) as a pale yellowish oil: IR (neat) 1720
cm-1; 1H NMR (300 MHz, CDCl3) δ 7.66-7.63 (m, 4H), 7.43-
7.34 (m, 7H), 6.02 (d, 1H, J ) 5.8 Hz), 3.65 (t, 2H, J ) 6.2
Hz), 2.28 (d, 1H, J ) 18.5 Hz), 2.10 (d, 1H, J ) 18.5 Hz), 1.60-
1.20 (m, 6H), 1.18 (s, 3H), 1.04 (s, 9H); MS m/ z 349 (M+
-
tBu). Anal. Calcd for C26H34O2Si: C, 76.80; H, 8.43. Found:
C, 76.57; 8.47.
4-[5-(ter t-Bu t yld ip h en ylsiloxy)p en t yl]-4-m et h yl-2-cy-
clop en ten -1-on e (12). Similarly, 10 (1.0 g, 2.06 mmol) was
transformed into 12 (810 mg, 94%) as a pale yellowish oil: IR
(neat) 1720 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.69-7.64 (m,
4H), 7.64-7.34 (m, 7H), 6.02 (d, 1H, J ) 5.5 Hz), 3.64 (t, 2H,
J ) 6.3 Hz), 2.27 (d, 1H, J ) 18.7 Hz), 2.09 (d, 1H, J ) 18.7
Hz), 1.61-1.20 (m, 8H), 1.19 (s, 3H), 1.04 (s, 9H); MS m/ z
363 (M+ - tBu). Anal. Calcd for C27H36O2Si: C, 77.09; H, 8.63.
Found: C, 77.06; H, 8.63.
4-(4-Hyd r oxybu tyl)-4-m eth yl-2-cyclop en ten -1-on e (13).
A mixture of 11 (1.23 g, 3.02 mmol) and 1.0 M Bu4NF in THF
(4.54 mL, 4.54 mmol) in dry THF (20 mL) was stirred for 2 h
at rt. After dilution with Et2O, the mixture was washed with
brine, dried (Na2SO4), and evaporated to give a residue, which
was purified by column chromatography on silica gel. Elution
with AcOEt-hexane (3:7 v/v) provided 13 (422 mg, 88%) as a
(()-(1S*,2R*,6S*,7R*)-5-[4-(ter t-Bu tyld ip h en ylsiloxy)-
p en tyl]tr icyclo[5.2.1.02,6]d eca -4,8-d ien -3-on e (8). Using
the same procedure as above, 8 (4.49 g, 72%) was prepared
from 6 (2.0 g, 13.4 mmol) as a colorless oil: IR (neat) 1700
cm-1; 1H NMR (300 MHz, CDCl3) δ 7.71-7.63 (m, 4H), 7.46-
7.34 (m, 6H), 5.98 (dd, 1H, J ) 5.8, 2.7 Hz), 5.75 (dd, 1H, J )
5.8, 2.7 Hz), 5.68 (br s, 1H), 3.67 (t, 1H, J ) 6.3 Hz), 3.28-
3.21 (m, 1H), 3.18 (br s, 1H), 3.01-2.94 (m, 1H), 2.87-2.77
(m, 1H), 2.30-2.18 (m, 2H), 1.79-1.71 (m, 1H), 1.65-1.35 (m,
1
colorless oil: IR (neat) 3400, 1710 cm-1; H NMR (300 MHz,
CDCl3) δ 7.44 (d, 1H, J ) 5.5 Hz), 6.04 (d, 1H, J ) 5.5 Hz),
3.65 (t, 2H, J ) 6.5 Hz), 2.32 (d, 1H, J ) 18.7 Hz), 2.13 (d, 1H,
J ) 18.7 Hz), 1.86-1.24 (m, 7H), 1.22 (s, 3H); MS m/ z 168
(M+). Anal. Calcd for C10H16O2: C, 71.39; H, 9.59. Found:
C, 71.62; H, 9.69.
4-(5-Hydr oxypen tyl)-4-m eth yl-2-cyclopen ten -1-on e (14).
Using the same method as above, 12 (1.24 g, 2.95 mmol) was
transformed into 14 (506 mg, 94%) as a colorless oil: IR (neat)
8H), 1.05 (s, 9H); HRMS calcd for C27H29O2Si (M+
413.1935, found 413.1911.
-
tBu)
1
3400, 1710 cm-1; H NMR (300 MHz, CDCl3) δ 7.44 (d, 1H, J
) 5.5 Hz), 6.03 (d, 1H, J ) 5.5 Hz), 3.62 (t, 2H, J ) 6.6 Hz),
2.30 (d, 1H, J ) 18.7 Hz), 2.21 (d, 1H, J ) 18.7 Hz), 1.79 (br
s, 1H), 1.60-1.23 (m, 8H), 1.21 (s, 3H); MS m/ z 182 (M+). Anal.
Calcd for C11H18O2: C, 72.49; H, 9.95. Found: C, 72.65; H,
9.74.
(()-(1S *,2R *,5R *,6S *,7R *)-5-[4-(t er t -Bu t yld ip h e n yl-
siloxy)bu tyl]-5-m eth yltr icyclo[5.2.1.02,6]dec-8-en -3-on e (9).
To a stirred mixture of CuI (2.5 g, 13.13 mmol) in dry Et2O
(15 mL) at 0 °C was added 1.04 M MeLi in Et2O (25.28 mL,
26.30 mmol). The mixture was then stirred for 30 min at the
same temperature. After the addition of BF3‚OEt2 (0.6 mL,
0.59 mmol) at -78 °C, followed by 20 min of stirring at -78
°C, to the stirred mixture at -78 °C was added a solution of 7
(2.0 g, 4.38 mmol) in dry Et2O (10 mL). The mixture was then
stirred for 30 min at the same temperature. After the addition
of BF3‚OEt2 (0.6 mL, 0.59 mmol), the mixture was further
stirred for 1 h at rt. After the addition of saturated NH4Cl,
the mixture was thoroughly extracted with Et2O. The com-
bined extracts were washed with brine, dried (Na2SO4), and
evaporated. The residue was purified by column chromatog-
raphy on silica gel. Elution with AcOEt-hexane (1:9 v/v)
4-[(4E)-5-(Met h oxyca r b on yl)-4-p en t en yl]-4-m et h yl-2-
cyclop en ten -1-on e (15). To a stirred solution of 13 (285 mg,
1.70 mmol) in dry CH2Cl2 (40 mL) at 0 °C were added 4 Å
molecular sieves (601 mg) and PCC (401 mg, 1.87 mmol). The
mixture was then stirred for 2 h at rt. After dilution with
Et2O, followed by filtration through Celite, evaporation of the
solvents gave the corresponding aldehyde, which was used in
the following reaction without purification.
A solution of the above product and Ph3PdCHCO2Me (737
mg, 2.20 mmol) in dry CH2Cl2 (15 mL) was stirred for 5 h at
rt. Evaporation of the solvent afforded a residue, which was
chromatographed on silica gel. Elution with AcOEt-hexane
(1:4 v/v) provided 15 (256 mg, 68%) as a colorless oil: IR (neat)
1
afforded 9 (1.50 g, 72%) as a colorless oil: IR (neat) cm-1; H
NMR (300 MHz, CDCl3) δ 7.70-7.65 (m, 4H), 7.45-7.35 (m,
6H), 6.16 (dd, 1H, J ) 5.5, 2.6 Hz), 6.02 (dd, 1H, J ) 5.5, 2.6
Hz), 3.70 (t, 2H, J ) 6.0 Hz), 3.20-3.13 (m, 1H), 3.04-2.95
(m, 2H), 2.55-2.49 (m, 1H), 1.88 (d, 1H, J ) 18.1 Hz), 1.75 (d,
1H, J ) 18.1 Hz), 1.90-1.18 (m, 8H), 1.06 (s, 9H), 0.94 (s, 3H);
1
1710, 1660 cm-1; H NMR (300 MHz, CDCl3) δ 7.42 (d, 1H, J
) 5.7 Hz), 6.92 (dt, 1H, J ) 15.7, 6.9 Hz), 6.05 (d, 1H, J ) 5.7
Hz), 5.82 (dt, 1H, J ) 15.7, 1.6 Hz), 3.73 (s, 3H), 2.30 (d, 1H,
J ) 18.4 Hz), 2.25-2.17 (m, 2H), 2.13 (d, 1H, J ) 18.4 Hz),
1.57-1.33 (m, 4H), 1.22 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
209.7, 172.6, 167.0, 148.5, 132.0, 121.6, 51.3, 47.6, 44.7, 39.7,
32.2, 26.0, 23.4; MS m/ z 222 (M+). Anal. Calcd for C13H18O3:
C, 70.25; H, 8.16. Found: C, 70.32; H, 8.33.
HRMS calcd for C27H31O2Si (M+
415.2076.
-
tBu) 415.2092, found
(()-(1S *,2R *,5R *,6S *,7R *)-5-[4-(t er t -Bu t yld ip h e n yl-
siloxy)p en tyl]-5-m eth yltr icyclo[5.2.1.02,6]d ec-8-en -3-on e
(10). Using the same procedure as above, 8 (4.47 g, 9.5 mmol)
4-[(5E)-6-(Meth oxyca r bon yl)-5-h exen yl]-4-m eth yl-2-cy-
clop en ten -1-on e (16). Using the same procedure as above,
14 (170 mg, 0.93 mmol) was converted into 16 (150 mg, 68%)
(15) Genard, S.; Patin, H. Bull. Soc. Chim. Fr. 1991, 397-406.
as a colorless oil: IR (neat) 1710, 1660 cm-1 1H NMR (300
;

6420 J . Org. Chem., Vol. 61, No. 18, 1996
Ihara et al.
MHz, CDCl3) δ 7.43 (d, 1H, J ) 5.5 Hz), 6.94 (dt, 1H, J ) 15.7,
6.9 Hz), 6.03 (d, 1H, J ) 5.5 Hz), 5.67 (dt, 1H, J ) 15.7, 1.4
Hz), 3.73 (s, 3H), 2.29 (d, 1H, J ) 18.4 Hz), 2.25-2.14 (m, 2H),
(()-(1S*,2S*,3R*,7R*,8R*)-(22) an d (()-(1S*,2R*,3R*,7R*,
8R*)-2-(Met h oxyca r b on yl)-7-m et h ylt r icyclo[5.3.0.03,8]-
d eca n -9-on e (23). (A) To a mixture of 15 (153 mg, 0.69
mmol), ZnCl2 (939 mg, 6.89 mmol), and Et3N (1.44 mL, 10.3
mmol) in dry toluene (7 mL) in a sealed tube was added TMSCl
(0.93 mL, 6.89 mmol). The mixture was then heated for 72 h
at 180 °C. After dilution with benzene, the resulting mixture
was washed with 10% HCl and brine, dried (Na2SO4), and
evaporated. Column chromatography of the residue on silica
gel with AcOEt-hexane (1:4 v/v) as the eluent gave a 3.6:1
mixture of 22 and 23 (61.6 mg, 40%) as a colorless oil, which
was separated by HPLC using Dynamax Microsorb silica (5
nm; 4 × 250 mm) with AcOEt-hexane (1:9 v/v; 1 mL‚min-1).
22: IR 1740, 1730 cm-1; 1H NMR (300 MHz, CDCl3) δ 3.68
(s, 3H), 3.09-3.03 (m, 1H), 3.05 (ddd, 1H, J ) 5.0, 2.7, 2.2
Hz), 2.68-2.62 (m, 1H), 2.51 (dt, 1H, J ) 4.7, 1.7 Hz), 2.32
(ddd, 1H, J ) 19.0, 4.7, 2.2 Hz), 2.04 (s, 1H), 1.82-1.46 (m,
7H), 1.07 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 216.8, 174.3,
61.1, 51.9, 49.5, 47.5, 47.2, 39.9, 36.5, 32.2, 28.1, 21.9, 18.0;
HRMS calcd for C13H18O3 (M+) 222.1255, found 222.1263.
23: IR (neat) 1740, 1730 cm-1; 1H NMR (300 MHz, CDCl3)
δ 3.64 (s, 3H), 3.22-3.15 (m, 1H), 2.61 (br s, 1H), 2.51 (d, 1H,
J ) 5.5 Hz), 2.34 (t, 1H, J ) 18.4 Hz), 1.99 (d, 1H, J ) 18.4
Hz), 1.90 (d, 1H, J ) 4.3 Hz), 1.87-1.54 (m, 6H), 0.98 (s, 3H);
HRMS calcd for C13H18O3 (M+) 222.1255, found 222.1263.
(B) To a stirred solution of 15 (60 mg, 0.27 mmol) in dry
ClCH2CH2Cl (10 mL) were added at 0 °C (TMS)2NH (0.086
mL, 0.41 mmol) and TMSI (0.046 mL, 0.32 mmol), and the
mixture was stirred for 1 h at rt. After dilution with Et2O,
the mixture was washed with saturated NH4Cl and brine,
dried (Na2SO4), and evaporated. The residue was purified by
column chromatography on silica gel with AcOEt-hexane (3:7
v/v) as the eluent, followed by HPLC using Dynamax Microsorb
silica (5 nm, 4 × 250 mm) with AcOEt-hexane (1:8 v/v; 1
mL‚min-1). The first fraction afforded one isomer of 25 (4.9
mg, 5%) as a colorless oil: IR (neat) 1735 cm-1; 1H NMR (300
MHz, CDCl3) δ 4.72 (dd, 1H, J ) 10.2, 9.1 Hz), 3.65 (s, 3H),
3.01 (dd, 1H, J ) 19.8, 8.8 Hz), 2.78-2.68 (m, 2H), 2.09 (dd,
1H, J ) 15.9, 9.1 Hz), 1.96-1.77 (m, 3H), 1.72-1.14 (m, 5H),
1.09 (s, 3H); HRMS calcd for C13H19IO3 (M+) 350.0377, found
350.0367.
2.12 (d, 1H, J ) 18.4 Hz), 1.59-1.23 (m, 6H), 1.21 (s, 3H); 13
C
NMR (75 MHz, CDCl3) δ 209.9, 172.9, 167.1, 149.1, 131.9,
121.2, 51.3, 47.6, 44.7, 40.1, 31.8, 28.3, 26.1, 24.1; MS m/ z
236 (M+). Anal. Calcd for C14H20O3: C, 71.16; H, 8.53.
Found: C, 70.99; H, 8.57.
4-[(5Z)-6-(Meth oxyca r bon yl)-5-h exen yl]-4-m eth yl-2-cy-
clop en ten -1-on e (17). Oxidation of 14 (100 mg, 0.55 mmol)
with PCC (3.90 mg, 1.81 mmol) in the presence of 4 Å
molecular sieves (585 mg) in dry CH2Cl2 (50 mL) as above gave
the aldehyde, which was used in the following reaction without
purification.
To a stirred solution of (CF3CH2O)2P(O)CH2CO2Me14 (0.17
mL, 0.82 mmol) and 18-crown-6 (725 mg, 2.75 mmol) in dry
THF (15 mL) at -78 °C was added 0.5 M KHMDS in toluene
(1.43 mL, 0.72 mmol). After the addition of the above aldehyde
in dry THF (10 mL), the mixture was stirred for 30 min at
the same temperature. After the addition with saturated NH4-
Cl, the mixture was thoroughly extracted with Et2O. The
extract was washed with brine, dried (Na2SO4), and evaporated
to afford a residue which was subjected to column chromatog-
raphy on silica gel. Elution with AcOEt-hexane (1:4 v/v)
provided 17 (71 mg, 55%) as a pale yellowish oil: IR (neat)
1
1720, 1650 cm-1; H NMR (300 MHz, CDCl3) δ 7.42 (d, 1H, J
) 5.5 Hz), 6.20 (dt, 1H, J ) 11.4, 7.7 Hz), 6.03 (d, 1H, J ) 5.5
Hz), 5.78 (dd, 1H, J ) 11.4, 1.9 Hz), 3.71 (s, 3H), 2.69-2.61
(m, 2H), 2.29 (d, 1H, J ) 18.7 Hz), 2.11 (d, 1H, J ) 18.7 Hz),
1.65-1.24 (m, 6H), 1.20 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
210, 173.1, 167.0, 150.3, 131.8, 119.6, 50.9, 47.7, 44.8, 40.1,
29.2, 28.6, 26.1, 24.5; HRMS calcd for C14H20O3 (M+) 236.1411,
found 236.1396.
Further elution gave 16 (4 mg, 3%) as a colorless oil, which
was identical with the authentic compound in all respects.
1-Me t h y l-5-[2-(m e t h o x y c a r b o n y l)m e t h y l]-2-(t er t -
bu tyld im eth ylsiloxy)bicyclo[4.3.0]n on a -6,8-d ien e (18). To
a stirred solution of 15 (30 mg, 0.14 mmol) and Et3N (0.094
mL, 0.86 mmol) in dry CH2Cl2 (3 mL) at 0 °C was added
TBDPSOTf (0.078 mmol, 0.34 mmol), and the mixture was
stirred for 2.5 h at rt. After dilution with CH2Cl2, the mixture
was washed with 10% KHSO4 and brine, dried (Na2SO4), and
evaporated to give a residue, which was purified by column
chromatography on silica gel. Elution with AcOEt-hexane
(1:19 v/v) afforded a 1:1.8 mixture of 18 (46 mg, 99%) as a
The second fraction gave the other isomer of 25 (4.9 mg,
5%) as a colorless oil: IR (neat) 1735 cm-1; 1H NMR (300 MHz,
CDCl3) δ 4.13 (dd, 1H, J ) 11.5, 8.5 Hz), 3.68 (s, 3H), 2.98-
2.82 (m, 2H), 2.69 (dd, J ) 19.5, 11.5 Hz), 2.49 (dd, 2H, J )
8.2, 4.1 Hz), 2.03 (br s, 1H), 1.56-1.27 (m, 6H), 1.23; HRMS
calcd for C13H19IO3 (M+) 350.0377, found 350.0356.
1
colorless oil: IR (neat) 1735, 1740 cm-1; H NMR (300 MHz,
CDCl3) δ 6.25 (d, 0.36H, J ) 5.5 Hz), 6.17 (d, 0.64H, J ) 5.5
Hz), 6.07 (d, 0.36H, J ) 5.5 Hz), 6.02 (d, 0.64H, J ) 5.5 Hz),
3.68 (s, 1.08 H), 3.66 (s, 1.92H), 3.54-3.45 (m, 0.64H), 3.26-
3.18 (m, 0.36H), 2.69-2.33 (m, 2H), 1.93-1.44 (m, 6H), 1.11
(s, 1.92H), 1.01 (s, 1.08H), 0.97 (s, 5.76H), 0.94 (s, 3.24H), 0.18
(s, 1.08H), 0.17 (s, 1.08H), 0.15 (s, 1.92H), 0.13 (s, 1.92H);
HRMS calcd for C19H32O3Si (M+) 336.2119, found 336.2013.
1-Met h yl-5-(2-h yd r oxyet h yl)b icyclo[4.3.0]n on -8-en -7-
on e (20). To a stirred solution of 18 (18.6 mg, 0.056 mmol)
in dry CH2Cl2 (10 mL) at -78 °C was added 0.98 M DIBALH
in hexane (0.21 mL, 0.20 mmol). The mixture was then stirred
for 1 h at -78 °C. After dilution with Et2O, followed by the
addition of H2O (0.21 mL), the mixture was stirred for 1.5 h
at rt. Filtration thorough Celite, followed by evaporation of
the solvents, gave a residue that was chromatographed on
silica gel. Elution with AcOEt-hexane (3:17 v/v) yielded 19
(9.5 mg, 56%) as a colorless oil.
The third fraction provided 22 (6.3 mg, 10%) as a colorless
oil, whose H NMR (300 MHz, CDCl3) spectrum was identical
with that of the above compound, prepared by method A.
1
The fourth fraction yielded 24 (22.2 mg, 37%) as a colorless
1
oil: IR (neat) 1740, 1700 cm-1; H NMR (300 MHz, CDCl3) δ
7.40 (d, 1H, J ) 5.8 Hz), 6.01 (d, 1H, J ) 5.8 Hz), 3.67 (s, 3H),
2.95 (t, 1H, J ) 15.1 Hz), 2.30 (dd, 1H, J ) 15.1, 9.3 Hz),
2.25-2.11 (m, 1H), 1.82-1.71 (m, 7H), 1.21 (s, 3H); HRMS
calcd for C13H18O3 (M+) 222.1255, found 222.1256.
(C) To a stirred solution of 15 (29 mg, 0.13 mmol) in dry
ClCH2CH2Cl (15 mL) at 0 °C were added (TMS)2NH (0.14 mL,
0.65 mmol) and 1 M Bu2BOTf in CH2Cl2 (0.39 mL, 0.39 mmol).
The mixture was then stirred for 3 h at rt. After dilution with
Et2O, the mixture was washed with saturated NH4Cl and
brine, dried (Na2SO4), and evaporated. Column chromatog-
raphy on silica gel with AcOEt-hexane (1:4 v/v) as the eluent
gave 22 (8.0 mg, 28%) as a colorless oil, which was identical
with the authentic sample in all respects.
(()-(1S *,2S *,3R *,8R *,9R *)-2-(Me t h ox yc a r b o n y l)-8-
m eth yltr icyclo[6.3.0.03,9]u n d eca n -10-on e (26). (A) A mix-
ture of 16 (45 mg, 0.19 mmol), Et3N (0.40 mL, 2.85 mmol),
ZnCl2 (260 mg, 1.90 mmol), and TMSCl (0.24 mL, 1.90 mmol)
in dry toluene (3 mL) was heated for 72 h at 180 °C in a sealed
tube. After dilution with benzene, the mixture was washed
with 10% HCl and brine, dried (Na2SO4), and evaporated to
afford a residue, which was subjected to column chromatog-
raphy on silica gel. Elution with AcOEt-hexane (1:4 v/v)
provided 26 (13 mg, 29%) as a colorless oil: IR (neat) 1740,
1735 cm-1; 1H NMR (300 MHz, CDCl3) δ 3.70 (s, 3H), 3.17 (ddd,
A mixture of 19 (9.5 mg, 0.029 mmol) and 1 M Bu4NF in
THF (0.046 mL, 0.046 mmol) in dry THF (10 mL) was stirred
for 2 h at rt. After dilution with Et2O, the mixture was washed
with brine, dried (Na2SO4), and evaporated. Column chroma-
tography of the residue on silica gel with AcOEt-hexane (2:3
v/v) as the eluent provided a 1:1.8 mixture of 20 (5.6 mg, 95%)
as a colorless oil: IR (neat) 3400, 1700 cm-1 1H NMR (300
;
MHz, CDCl3) δ 7.41 (d, 0.64H, J ) 5.8 Hz), 7.36 (d, 0.36H, J
) 5.8 Hz), 6.08 (d, 0.36H, J ) 5.8 Hz), 6.02 (d, 0.64H, J ) 5.8
Hz), 3.87-3.62 (m, 2H), 2.36-1.32 (m, 11H), 1.25 (s, 1.08H),
1.23 (s, 1.92H); HRMS calcd for C12H18O2 (M+) 194.1306, found
194.1309.

Construction of Copaborneol and Longiborneol Frameworks
J . Org. Chem., Vol. 61, No. 18, 1996 6421
1H, J ) 6.3, 4.1, 2.2 Hz), 2.56-2.49 (m, 1H), 2.44 (dt, 1H, J )
4.9, 1.9 Hz), 2.29 (dddd, 1H, J ) 18.7, 4.7, 2.2, 0.8 Hz), 2.44-
2.22 (m, 1H), 2.00 (d, 1H, J ) 18.7 Hz), 1.90-1.78 (m, 2H),
1.72-1.17 (m, 6H), 1.06 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
215.6, 174.7, 63.5, 51.9, 50.7, 49.2, 47.0, 39.3, 39.0, 38.4, 29.7,
26.5, 25.2, 24.0; HRMS calcd for C14H20O3 (M+) 236.1411, found
236.1426.
(B) Treatment of 16 (30 mg, 0.12 mmol) with (TMS)2NH
(0.046 mL, 0.21 mmol) and TMSI (0.027 mL, 0.19 mmol) in
ClCH2CH2Cl (5 mL) for 1 h at rt, followed by the similar
workup and purification as above, gave 26 (21 mg, 69%) as a
colorless oil, which was identical with the authentic compound,
prepared by method A, in all respects.
(C) Reaction of 16 (31 mg, 0.13 mmol) with (TMS)2NH (0.14
mL, 0.65 mmol) and 1.0 M Bu2BOTf in CH2Cl2 (0.39 mL, 0.39
mmol) in ClCH2CH2Cl (10 mL) for 3 h at rt, followed by the
similar workup and purification as the case of A, provided 26
(22 mg, 71%) as a colorless oil, which was identical with the
authentic compound in all respects.
(D) Treatment of 17 (20 mg, 0.085 mmol) with (TMS)2NH
(0.03 mL, 0.14 mmol) and TMSI (0.018 mL, 0.13 mmol) in dry
ClCH2CH2 (5 mL) for 1 h at rt, followed by the same workup
and purification procedure as above, yielded 26 (13 mg, 67%)
as a colorless oil, which was identical with the authentic
compound in all respects.
(E) Reaction of 17 (23 mg, 0.097 mmol) with (TMS)2NH (0.10
mL, 0.48 mmol) and 1.0 M Bu2BOTf in CH2Cl2 (0.29 mL, 0.29
mmol) in dry ClCH2CH2Cl (10 mL) for 3 h at rt, followed by
the same workup and purification as above, gave 26 (1.6 mg,
7%) as a colorless oil, which was identical with the authentic
compound in all respects.
Meth yl (2Z)- (28) a n d (2E)-6-(Ben zyloxy)-2-h exen a tes
(29). A mixture of 4-(benzyloxy)butan-1-ol16 (500 mg, 2.77
mmol), 4 Å molecular sieves (1 g), and PDC (1.25 g, 3.32 mmol)
in dry CH2Cl2 (15 mL) was stirred for 2 h at rt. After dilution
with Et2O, followed by filtration through Celite, evaporation
of the solvents gave the corresponding aldehyde, which was
used in the following reaction without purification.
After treatment of (CF3CH2O)2P(O)CH2CO2Me14 (0.76 mL,
3.59 mmol) with 0.5 M KHMDS in toluene (6.66 mL, 3.33
mmol) in the presence of 18-crown-6 (2.2 g, 8.32 mmol) in dry
THF (20 mL) for 30 min at -78 °C, to the resulting mixture
at -78 °C was added a solution of the above aldehyde in dry
THF (8 mL). After being stirred for 1.5 h at -78 °C, the
mixture was diluted with Et2O. The mixture was washed with
brine, dried (MgSO4), and evaporated. Column chromatogra-
phy on silica gel with AcOEt-hexane (15:85 v/v) as the eluent
gave 28 (473 mg, 73%) as a colorless oil: IR (neat) 1720, 1645
1
cm-1; H NMR (300 MHz, CDCl3) δ 7.36-7.27 (m, 5H), 6.25
(dt, 1H, J ) 11.5, 7.4 Hz), 5.79 (dt, 1H, J ) 11.5, 1.6 Hz), 4.50
(s, 2H), 3.70 (s, 3H), 3.51 (t, 2H, J ) 6.6 Hz), 2.80-2.71 (m,
2H), 1.83-1.73 (m, 2H); HRMS calcd for C14H19O3 (M+ + H)
235.1335, found 235.1286.
Further elution gave the (E)-isomer 29 (41 mg, 6.3%) as a
1
colorless oil: IR (neat) 1720, 1655 cm-1; H NMR (300 MHz,
CDCl3) δ 7.37-7.27 (m, 5H), 6.98 (dt, 1H, J ) 15.7, 7.0 Hz),
5.83 (dt, 1H, J ) 15.7, 1.6 Hz), 4.50 (s, 2H), 3.73 (s, 3H), 3.49
(t, 2H, J ) 6.3 Hz), 2.37-2.27 (m, 2H), 1.83-1.73 (m, 2H);
HRMS calcd for C14H19O3 (M+ + H) 235.1335, found 235.1361.
Isom er iza tion of 28. To a stirred solution of 28 (40 mg,
0.17 mmol) in dry ClCH2CH2Cl (5 mL) at 0 °C were added
(TMS)2NH (0.055 mL, 0.26 mmol) and TMSI (0.032 mL, 0.22
mmol), and the mixture was stirred for 1 h at rt. After dilution
with Et2O, the mixture was washed with saturated NH4Cl,
5% Na2S2O3, and brine, dried (MgSO4), and evaporated.
Column chromatography on silica gel with AcOEt-hexane (1:4
v/v) provided the (E)-isomer 29, whose 1H NMR (300 MHz,
CDCl3) spectrum was identical with that of the authentic
sample. No (Z)-isomer 28 was detected on the 1H NMR
spectrum.
Ack n ow led gm en t. We thank Mr. K. Kawamura,
Ms. K. Mushiake, Ms. M. Suzuki, Ms. A. Satoh, and Ms.
Y. Maehashi of this Institute for microanalyses, spectral
measurements, and the preparation of the paper. This
research was supported, in part, by J SPS Research
Fellowships for Young Scientists to K.M.
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra of
compounds 7-10, 17, 18, 20, 22, 23, 26, 28, and 29 (12 pages).
This material is contained in libraries on microfiche, im-
mediately 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.
(16) Dawson, M. I.; Vasser, M. J . Org. Chem. 1977, 42, 2783-2785.
J O960698S