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Synthetic studies on rabdosia diterpene lactones II: The synthesis of 15-desoxyeffusin
Tetrahedron Letters,Vo1.27,No.33,pp Printed in Great Britain
0040-4039/86 $3.00 + .OO Pergamon Journals Ltd.
3927-3930,1986
SYNTHETIC STUDIES ON RABDOSIA DITERPENE LACTONES II : THE SYNTHESIS OF 15-DESOXYEFFUSIN M.J. Research
School
of
Kenny,
Chemistry,
In the
which
preceding
was envisaged
transformation products
of
2 and 4,
we outlined
C 23 and effusin
as a key 1 into
15-desoxy
in
the
first
subjected of
the
gibberellins,7
was treated
reconstituted
Hydroxylation butyldimethylsilyl mask the acid
the
in
derived
preparation
the
plan.
to
examined.
synthesis
of
of
ACT
the
the
We now report
3 and 5 corresponding
to
reaction
LDA to
afford
the C(17)
the
(+)-
Rabdosia
ester
1,
the natural
enol during
7 was cyclised
homogeneous
to
give
event,
to
to
The mixture
subsequent
In the
affording
had proven
C(3)-C(4)
0x0 lactone
efficiently.11
3927
product
10,
effective
m.p. of
145-146OC,
of to
but
in
the
lactonea the
synthesis 8,
the
C(7)
in view enol
of
m.p.
composite
derived
of
indicated
In a variation
bromide
carbonyl
146-147.5’C. the
treatment afforded
crude
6. 596
and then
oxidation8
procedure
and the
mixture
bond formation
11 , m.p.
as
enone
be so
a 3:l
was completed
was converted
transformations. this
group)
by “Red-Al”
process,
by osmium tetroxide ether9
4 R=O 5 R=H,
methylene
1 was reduced
which
effect
the
R&J
3 R=H,
Thus,
propionate
effected
(TBS)
for
synthesis
OH 2
‘9
respectively.
with
was then
/
g-elimination
Michael
new hydroxylto
was also
total
the
derivatives
from
the Scheme.
and 126.5-127.5’C,
9 which
(apart
an acid-catalysed
intramolecular
92-93’
group
skeleton of
Canberra,
12
AcO
part to
GPO Box 4,
the
respectively.
1
The kaurane
Sethi
and described
a strategy 44,
intermediate
the
and S.P.
ester 1 was transformed by a sequence of intramolecular reactions into the pentacyclic lactone 10 from which the of longikaurin C 2 and effusin 4 were then prepared.
Letter’
longikaurin
Mander*
Australian National University, 26d1, Australia
The tricyclic summary: Michael and alkylation 15-desoxy derivatives
diterpenes2
L.N.
6Rtof
the
ether
12 more directly
need
to
11 by perand
3928
1
Id
i
AcO
,,i
15
ial Na Al(OCHZCH20Me)2H2(3.5equiv), PhMe, 25'C, lh. (cl (EtCO),O, Py, DMAP, 25'C, 5h. MeOH, O.Sh. 10 min.
(d) KH(1.2 equiv),
60%
140TBDMS
(bl pMePhS03H, PhH, ZS'C, lh. DMF, -30°C, 2h.
lel NaB(CN)H3,
(fl t-BuSiMe20S02CF3(1.5equiv), 2,6-lutidine(2equiv), CZCH2CH Cl, 25*C, 2S°C, lh; Me J O-, lOO"C, 3h. (i) LDA (1.4 equiv), THF, -2O"C, O.Sh.
(g) Me2CHCH(Me12BH2(3equivl, diglyme, O'C, 10 min;
Ihl Ph3P(2.2 equivl, CBr(l.1 equiv), Py. Ij) Bu4fiF-16 equivl, THF, 25'C, 5h.
Ikl (PyHI2&207(3.0 equivl, CH2C12, ZS"C, 16h.
(1) t-BuSiMe20S02CF3(1.5equivl, Et3N, ZS"C, 12h. N-oxide (4 equivl, t-BuOH, H20, 25'C, 1Oh.
(ml O~O~(0.05 equivl, N-methylmorpholine
(nl mCZPhCO$Cl.Z equivl, CH2C12, ZS"C, 30 tin.
(al t-BuSiMe20S02CF3(4equivl, iPr2NEtll.S equivl, DMAP(catalytic),ClCH2CH2Cl, 25OC, 6h. (pl KOH, MeOH, 25OC, lh. 25OC, 2h.
(s) Ac20, Py.
PhMe, 25OC, 0.5h.
(r) LiAlH4(0.7 equivl, THF, (filtered solution), (tl Me2BBrlZ equiv), Et3N, -?8OC, 5 min. (u) Ph>MeBp-, iAmOK, (q) CH2N2, Et20.
(vl as for j, but 10 min.
Iwl H5Z06, Et20, 10 min.
3929
We hoped 20+7
treatment)
compatible acetal
with
carbon
doublet
the
for
longikaurin
of
the
12 (G
non gave
to
confirmed
by single
this
congeners arising
our synthetic
to the
crystal
function
X-ray
analysis
(Figure
C(9),
13C-NMR spectra
were
and it3
which
C(10)
&.
with
had been
smaller
than
that
for
of
observed
consistent
the
with
a boat
that
reported
carbonyl
a
for
was due
function
derivatives
also
as a with
discrepancy
in
the
more closely
the hemi-acetal
which
a
by an
commensurate
the C(15)
reported
11,
replacement
and therefore
Formation
2
of
(6 209.9)
J=4Hz,
bonding
have been
formation
occurred:
seemed reasonable
from hydrogen
to
(following
4Hz was rather
it
constants
with
of
m.p.
from H(6)
a doublet
lead
145-146’C,
coupling
value
12 would
product,
had indeed
2 (6-7Hz),
at C(5),
in
the
resonance
intermediate.’
assignments
of
trans-diaxial
rise
4Hz coupling
analogous
function
carbonyl
Although
8.
differences
stereochemical
that C(7)
The ‘H-methine
ring
compounds:
lactone
examination
the
11 and
C 23 and its
torsional
latter
in
substituent)
conformation
of
indicated
loss
(6 97.6).
(J-8.6Hz)
6B-oxygen
hydrolysis
and spectroscopic
hemiacetal,
diazomethane
to
that
13 was finally
established
that
the
earlier
had been made correctly.‘3
Figure 1 Ortep plot of ester 13 (50% probability)
Reduction acetate
14,
methoxymethyl in
the
m.p.
groups of
207-209OC,
spectra group
induced
of
which
into
to
an aldehyde, with
resolution
which
acid, of
for
m.p.
structure
yet
remaining
us to
15 which
and acetylation
the
removal
unmask the to
the
C(17)
C(17)
was desilylated
gave
of hydroxyl
ketone to
15,
afford
(MS, HRMS, IR,
and NMR) were fully
the structural
assignment
118-119.S°C,
(6 9.69,
d,
The introduction able
to apply
been realised. problem
for
the product
5.‘7
we have been
has not
this
enabled
gave
evidence
aluminum hydride procedure
of
constants
Further
in agreement
and kaurenoic
successful
‘li then
spectroscopic
3.16
reported
methylenation
3 or 5 by procedures18
gibberellins
synthetic
whose
cleavage
were
by lithium
Oxidation
TBDMS ether.
by Wittig
structure
group
The recently
dimethylbromoborane
~(6)
followed
with
by periodate
methoxycarbonyl
with the
200-201°C
m.p.
consistent
the
152.5-153.5’C.
presence
product,
the
of
m.p.
in the
carbonyl
to
We expect
paper
the
a C(15)
satisfactorily
however. full
was obtained
J=4Hz), of
a
to
describing
report
on
this
endeavour.
Acknowledgements: The execution provided
by Bruce
longikaurin sample L.
of
of
this
Twitchin.
study
was made
We are
also
C and ‘3C-NMR spectroscopic oridonin,
Lombard0
for
to
advice
Dr A.C. on the
Willis
possible
most data
for
intramolecular
only
grateful
for
this
the X-ray Michael
through
to Professor compound,
crystal reaction.
to
structure
the
technical
T.
Fujlta
Professor
support for
a sample
E. Fujita
determination
for
and to
of a Dr
3930
References 1. 2.
and Footnotes
M.J.
Kenny,
E. Fujita
and M.
Verlag, 3.
L.N. Mander,
Progress
Node,
New York,
T. Fujita,
and S.P.
1984,
Y. Takeda,
Sethi,
in the Chemistry
4.
I.
5.
J. -Cf. C. Stork and R.L. Danheizer, biz(methoxyethoxy)aluminum dihydride this
6.
T. Izobe,
1,3,5
Heterocyclez,
kaurane
L. Lombardo, Cossey,
All
skeleton.
Org.
Mander,
8.
J.P.
McCormick,
9.
L.N. Mander and S.P.
10.
E.J.
11.
cr.
communication.
Products,
Vol.
46,
Springer
16, 227.
Chem. Sot. 1973,
38,
(Aldrich
Chemical
racemates
and are
CmmUn.,
Chem.
Co.)
1980,
1206.
Only “Red-Al”,
1775.
gave acceptable
Corey,
J.
and J.V.
Org.
Chem.,
1983,
W. Tomasik,
sodium
results
in
Tetrahedron
reaction
is
expected
13.
X-ray
normally T. Fujita,
Analysis:
13.116(2);, (l)O,
i3,
2656 observed
thermal
ellipsoid are
of arbitrary
and H.E.
C. Yoakim,
15.
E. J.
and G. Schmidt,
16.
‘H NMR (200 MHZ, CDC13): 6 l.l1,8,3H,Me(18);
with
Tetrahedron
6 -2.6,cTBDMS);
J.
Lett.,
30.6,Ccl);
31.6.C(14);
48.8,C(8);
53.3.C(5);
104.6,C(17); Cal&.
4.89,4.99,6z,2xlH,CH2(17); 374.2092. Dolan,
and
22,
3455.
1974, This
space
group
6 = 104.36(l)‘.
Chem.,
1984,
2 =
on Philips
reflections
to final for
Pi,
Y = 102.55
collected
3851 unique
except
A.
of
3423.
triclinic,
data
4319;
type
with
R-0.042.
the
hydrogen
The atoms
49,
3912.
399. 3.87,d,J=5Hz.lH,H(6);
4.75,4.93.b8,2xlH,CH2(17). 18.4,C(ll);
2l.O(OAc);
35.8,C(3); 57.8,C(9);
35.9,C(4); 66.5,c(l9);
171 .l,(OAc):
13C-
26.0,cTBDMS); 37.1,CllO); 66.6,C(20);
urnax 3580,3300.1730,1655
C22H32O5: 376.2250.
‘H NMR (200 MHZ. CDC13): 6 l.l8,8,3H,Me(l8); 4.03.4.21,ABq,J=12Hz,2H,CH2(19);
ethers.
levels
1979,
16O.O,C(l6);
for
TBDMSenol 1966,
22,
Lett., 3427.
2.08,s,3H,OAc;
15.8,C(2);
44.8,C(15); 99.O,C(7);
A.L.
22, 607.
1981,
40,
in the
Org.
30.2,C(l2);
HRMS 376.2236.
1975,
by MULTANand refined
37.4,C(13); cm-’ .
6626;
L. Lombard0
1981,
Lett.,
a = 107.36(l)‘, cm-3 . Intensity
26.5,C(l8); 74.2.C(6);
Lett.,
Tetrahedron,
4.21,4.44,ABq,J=l2Hz,2H,CH2(20);
NMR(6-TBDMS ether):
102,
4383;
radius.
Morton,
Y. Guindon,
3.89,z,2H,CH2(lg);
poorly
shows 50% probability
drawn as spheres
and
25, 5953.
(A(Kal)=0.70930i:
Solved
14.
Corey
Chem.,
(Z=2) = 1.187g
(2>3o(i)).
diagram
HRMS data, assignments.
1980, 1980,
Tetrahedron
Org.
and N. Ito,
MO Ku radiation
28<45’,
which
J.
2 = 10.636(2)x,
&,Ic
PWllOO diffractometer,
1984,
from ether-hexane
b = 11.995(2)1,
1 = 1468.4
Lett.,
Tetrahedron
Lett.,
to proceed
K. Fuji,
crystallized
structural
Am. Chem.%.,
and D.R. Peligrina,
and H.W. Pinnick,
E. Fujita,
to the
by correct
with
and D.H. Hua, Tetrahedron
M.A. Vazquez,
according
48, 2298.
R.H. Reusz,
12.
J.
Tetrahedron
and M.W. Johnson,
Sethi,
H. Cho, C. Rucker,
G.M. Rubottom,
consistent
Turner,
and L.N. Mander,
numbered
were characterised
were fully
Hazsner,
S.C.
J.
Chem.,
compounds
which
L.N. Mander,
L. Lombardo.
L.N.
18.
1981,
and T. Kubota,
and 6-15 represent
IR, NMR and mass spectra
17.
of Natural
preceding
transformation.
Structures complete
7.
Lett.,
pp.77-157.
and T. Shingu,
Kubo, T. Kamikawa,
Tetrahedron
2.11.s,3H,OAc;
2.38,d,lH,J-4Hz,H(5);
4.52,4.62,ABq,J=12Hz,2H,CH2(20); 9.89,d,J=4Hz,lH.H(6).
CaIcd. for C22H3005: 374.2093. D.W. Holdup, M. Hutchinson, and J.
651.
(Received in UK 14 May 1986)
vmax 2710,1730,1710,1655 MacMillan,
J.
Chem. Sot.
cm-‘. Perkin
HRMS I,
1985,
0040-4039/86 $3.00 + .OO Pergamon Journals Ltd.
3927-3930,1986
SYNTHETIC STUDIES ON RABDOSIA DITERPENE LACTONES II : THE SYNTHESIS OF 15-DESOXYEFFUSIN M.J. Research
School
of
Kenny,
Chemistry,
In the
which
preceding
was envisaged
transformation products
of
2 and 4,
we outlined
C 23 and effusin
as a key 1 into
15-desoxy
in
the
first
subjected of
the
gibberellins,7
was treated
reconstituted
Hydroxylation butyldimethylsilyl mask the acid
the
in
derived
preparation
the
plan.
to
examined.
synthesis
of
of
ACT
the
the
We now report
3 and 5 corresponding
to
reaction
LDA to
afford
the C(17)
the
(+)-
Rabdosia
ester
1,
the natural
enol during
7 was cyclised
homogeneous
to
give
event,
to
to
The mixture
subsequent
In the
affording
had proven
C(3)-C(4)
0x0 lactone
efficiently.11
3927
product
10,
effective
m.p. of
145-146OC,
of to
but
in
the
lactonea the
synthesis 8,
the
C(7)
in view enol
of
m.p.
composite
derived
of
indicated
In a variation
bromide
carbonyl
146-147.5’C. the
treatment afforded
crude
6. 596
and then
oxidation8
procedure
and the
mixture
bond formation
11 , m.p.
as
enone
be so
a 3:l
was completed
was converted
transformations. this
group)
by “Red-Al”
process,
by osmium tetroxide ether9
4 R=O 5 R=H,
methylene
1 was reduced
which
effect
the
R&J
3 R=H,
Thus,
propionate
effected
(TBS)
for
synthesis
OH 2
‘9
respectively.
with
was then
/
g-elimination
Michael
new hydroxylto
was also
total
the
derivatives
from
the Scheme.
and 126.5-127.5’C,
9 which
(apart
an acid-catalysed
intramolecular
92-93’
group
skeleton of
Canberra,
12
AcO
part to
GPO Box 4,
the
respectively.
1
The kaurane
Sethi
and described
a strategy 44,
intermediate
the
and S.P.
ester 1 was transformed by a sequence of intramolecular reactions into the pentacyclic lactone 10 from which the of longikaurin C 2 and effusin 4 were then prepared.
Letter’
longikaurin
Mander*
Australian National University, 26d1, Australia
The tricyclic summary: Michael and alkylation 15-desoxy derivatives
diterpenes2
L.N.
6Rtof
the
ether
12 more directly
need
to
11 by perand
3928
1
Id
i
AcO
,,i
15
ial Na Al(OCHZCH20Me)2H2(3.5equiv), PhMe, 25'C, lh. (cl (EtCO),O, Py, DMAP, 25'C, 5h. MeOH, O.Sh. 10 min.
(d) KH(1.2 equiv),
60%
140TBDMS
(bl pMePhS03H, PhH, ZS'C, lh. DMF, -30°C, 2h.
lel NaB(CN)H3,
(fl t-BuSiMe20S02CF3(1.5equiv), 2,6-lutidine(2equiv), CZCH2CH Cl, 25*C, 2S°C, lh; Me J O-, lOO"C, 3h. (i) LDA (1.4 equiv), THF, -2O"C, O.Sh.
(g) Me2CHCH(Me12BH2(3equivl, diglyme, O'C, 10 min;
Ihl Ph3P(2.2 equivl, CBr(l.1 equiv), Py. Ij) Bu4fiF-16 equivl, THF, 25'C, 5h.
Ikl (PyHI2&207(3.0 equivl, CH2C12, ZS"C, 16h.
(1) t-BuSiMe20S02CF3(1.5equivl, Et3N, ZS"C, 12h. N-oxide (4 equivl, t-BuOH, H20, 25'C, 1Oh.
(ml O~O~(0.05 equivl, N-methylmorpholine
(nl mCZPhCO$Cl.Z equivl, CH2C12, ZS"C, 30 tin.
(al t-BuSiMe20S02CF3(4equivl, iPr2NEtll.S equivl, DMAP(catalytic),ClCH2CH2Cl, 25OC, 6h. (pl KOH, MeOH, 25OC, lh. 25OC, 2h.
(s) Ac20, Py.
PhMe, 25OC, 0.5h.
(r) LiAlH4(0.7 equivl, THF, (filtered solution), (tl Me2BBrlZ equiv), Et3N, -?8OC, 5 min. (u) Ph>MeBp-, iAmOK, (q) CH2N2, Et20.
(vl as for j, but 10 min.
Iwl H5Z06, Et20, 10 min.
3929
We hoped 20+7
treatment)
compatible acetal
with
carbon
doublet
the
for
longikaurin
of
the
12 (G
non gave
to
confirmed
by single
this
congeners arising
our synthetic
to the
crystal
function
X-ray
analysis
(Figure
C(9),
13C-NMR spectra
were
and it3
which
C(10)
&.
with
had been
smaller
than
that
for
of
observed
consistent
the
with
a boat
that
reported
carbonyl
a
for
was due
function
derivatives
also
as a with
discrepancy
in
the
more closely
the hemi-acetal
which
a
by an
commensurate
the C(15)
reported
11,
replacement
and therefore
Formation
2
of
(6 209.9)
J=4Hz,
bonding
have been
formation
occurred:
seemed reasonable
from hydrogen
to
(following
4Hz was rather
it
constants
with
of
m.p.
from H(6)
a doublet
lead
145-146’C,
coupling
value
12 would
product,
had indeed
2 (6-7Hz),
at C(5),
in
the
resonance
intermediate.’
assignments
of
trans-diaxial
rise
4Hz coupling
analogous
function
carbonyl
Although
8.
differences
stereochemical
that C(7)
The ‘H-methine
ring
compounds:
lactone
examination
the
11 and
C 23 and its
torsional
latter
in
substituent)
conformation
of
indicated
loss
(6 97.6).
(J-8.6Hz)
6B-oxygen
hydrolysis
and spectroscopic
hemiacetal,
diazomethane
to
that
13 was finally
established
that
the
earlier
had been made correctly.‘3
Figure 1 Ortep plot of ester 13 (50% probability)
Reduction acetate
14,
methoxymethyl in
the
m.p.
groups of
207-209OC,
spectra group
induced
of
which
into
to
an aldehyde, with
resolution
which
acid, of
for
m.p.
structure
yet
remaining
us to
15 which
and acetylation
the
removal
unmask the to
the
C(17)
C(17)
was desilylated
gave
of hydroxyl
ketone to
15,
afford
(MS, HRMS, IR,
and NMR) were fully
the structural
assignment
118-119.S°C,
(6 9.69,
d,
The introduction able
to apply
been realised. problem
for
the product
5.‘7
we have been
has not
this
enabled
gave
evidence
aluminum hydride procedure
of
constants
Further
in agreement
and kaurenoic
successful
‘li then
spectroscopic
3.16
reported
methylenation
3 or 5 by procedures18
gibberellins
synthetic
whose
cleavage
were
by lithium
Oxidation
TBDMS ether.
by Wittig
structure
group
The recently
dimethylbromoborane
~(6)
followed
with
by periodate
methoxycarbonyl
with the
200-201°C
m.p.
consistent
the
152.5-153.5’C.
presence
product,
the
of
m.p.
in the
carbonyl
to
We expect
paper
the
a C(15)
satisfactorily
however. full
was obtained
J=4Hz), of
a
to
describing
report
on
this
endeavour.
Acknowledgements: The execution provided
by Bruce
longikaurin sample L.
of
of
this
Twitchin.
study
was made
We are
also
C and ‘3C-NMR spectroscopic oridonin,
Lombard0
for
to
advice
Dr A.C. on the
Willis
possible
most data
for
intramolecular
only
grateful
for
this
the X-ray Michael
through
to Professor compound,
crystal reaction.
to
structure
the
technical
T.
Fujlta
Professor
support for
a sample
E. Fujita
determination
for
and to
of a Dr
3930
References 1. 2.
and Footnotes
M.J.
Kenny,
E. Fujita
and M.
Verlag, 3.
L.N. Mander,
Progress
Node,
New York,
T. Fujita,
and S.P.
1984,
Y. Takeda,
Sethi,
in the Chemistry
4.
I.
5.
J. -Cf. C. Stork and R.L. Danheizer, biz(methoxyethoxy)aluminum dihydride this
6.
T. Izobe,
1,3,5
Heterocyclez,
kaurane
L. Lombardo, Cossey,
All
skeleton.
Org.
Mander,
8.
J.P.
McCormick,
9.
L.N. Mander and S.P.
10.
E.J.
11.
cr.
communication.
Products,
Vol.
46,
Springer
16, 227.
Chem. Sot. 1973,
38,
(Aldrich
Chemical
racemates
and are
CmmUn.,
Chem.
Co.)
1980,
1206.
Only “Red-Al”,
1775.
gave acceptable
Corey,
J.
and J.V.
Org.
Chem.,
1983,
W. Tomasik,
sodium
results
in
Tetrahedron
reaction
is
expected
13.
X-ray
normally T. Fujita,
Analysis:
13.116(2);, (l)O,
i3,
2656 observed
thermal
ellipsoid are
of arbitrary
and H.E.
C. Yoakim,
15.
E. J.
and G. Schmidt,
16.
‘H NMR (200 MHZ, CDC13): 6 l.l1,8,3H,Me(18);
with
Tetrahedron
6 -2.6,cTBDMS);
J.
Lett.,
30.6,Ccl);
31.6.C(14);
48.8,C(8);
53.3.C(5);
104.6,C(17); Cal&.
4.89,4.99,6z,2xlH,CH2(17); 374.2092. Dolan,
and
22,
3455.
1974, This
space
group
6 = 104.36(l)‘.
Chem.,
1984,
2 =
on Philips
reflections
to final for
Pi,
Y = 102.55
collected
3851 unique
except
A.
of
3423.
triclinic,
data
4319;
type
with
R-0.042.
the
hydrogen
The atoms
49,
3912.
399. 3.87,d,J=5Hz.lH,H(6);
4.75,4.93.b8,2xlH,CH2(17). 18.4,C(ll);
2l.O(OAc);
35.8,C(3); 57.8,C(9);
35.9,C(4); 66.5,c(l9);
171 .l,(OAc):
13C-
26.0,cTBDMS); 37.1,CllO); 66.6,C(20);
urnax 3580,3300.1730,1655
C22H32O5: 376.2250.
‘H NMR (200 MHZ. CDC13): 6 l.l8,8,3H,Me(l8); 4.03.4.21,ABq,J=12Hz,2H,CH2(19);
ethers.
levels
1979,
16O.O,C(l6);
for
TBDMSenol 1966,
22,
Lett., 3427.
2.08,s,3H,OAc;
15.8,C(2);
44.8,C(15); 99.O,C(7);
A.L.
22, 607.
1981,
40,
in the
Org.
30.2,C(l2);
HRMS 376.2236.
1975,
by MULTANand refined
37.4,C(13); cm-’ .
6626;
L. Lombard0
1981,
Lett.,
a = 107.36(l)‘, cm-3 . Intensity
26.5,C(l8); 74.2.C(6);
Lett.,
Tetrahedron,
4.21,4.44,ABq,J=l2Hz,2H,CH2(20);
NMR(6-TBDMS ether):
102,
4383;
radius.
Morton,
Y. Guindon,
3.89,z,2H,CH2(lg);
poorly
shows 50% probability
drawn as spheres
and
25, 5953.
(A(Kal)=0.70930i:
Solved
14.
Corey
Chem.,
(Z=2) = 1.187g
(2>3o(i)).
diagram
HRMS data, assignments.
1980, 1980,
Tetrahedron
Org.
and N. Ito,
MO Ku radiation
28<45’,
which
J.
2 = 10.636(2)x,
&,Ic
PWllOO diffractometer,
1984,
from ether-hexane
b = 11.995(2)1,
1 = 1468.4
Lett.,
Tetrahedron
Lett.,
to proceed
K. Fuji,
crystallized
structural
Am. Chem.%.,
and D.R. Peligrina,
and H.W. Pinnick,
E. Fujita,
to the
by correct
with
and D.H. Hua, Tetrahedron
M.A. Vazquez,
according
48, 2298.
R.H. Reusz,
12.
J.
Tetrahedron
and M.W. Johnson,
Sethi,
H. Cho, C. Rucker,
G.M. Rubottom,
consistent
Turner,
and L.N. Mander,
numbered
were characterised
were fully
Hazsner,
S.C.
J.
Chem.,
compounds
which
L.N. Mander,
L. Lombardo.
L.N.
18.
1981,
and T. Kubota,
and 6-15 represent
IR, NMR and mass spectra
17.
of Natural
preceding
transformation.
Structures complete
7.
Lett.,
pp.77-157.
and T. Shingu,
Kubo, T. Kamikawa,
Tetrahedron
2.11.s,3H,OAc;
2.38,d,lH,J-4Hz,H(5);
4.52,4.62,ABq,J=12Hz,2H,CH2(20); 9.89,d,J=4Hz,lH.H(6).
CaIcd. for C22H3005: 374.2093. D.W. Holdup, M. Hutchinson, and J.
651.
(Received in UK 14 May 1986)
vmax 2710,1730,1710,1655 MacMillan,
J.
Chem. Sot.
cm-‘. Perkin
HRMS I,
1985,