- Email: [email protected]
The n→π cd of αβ-unsaturated lactones
Tetrahedron
No.
Letters
17,
pp 1669
- 1672,
1972.
Printed
Pergamon Press.
in Great Britain.
THE n-+x* CD OF aB-UNSATURATEDLACTONES
Division
(Received
Results of
(2,3),
is
about
0.51
plane
as C5.
preserved.
in DK 28 February
from X-ray
the as-unsaturated normally from this
A.F. Beecham of Chemical Physics, CSIRO, P.O. Box 160, Clayton, Victoria, Australia 3168.
structure
g-lactone I,
or its plane
ring,
accepted
analyses
suggest
whether
enantiomer, and the ring
Co-planarity
1972;
of
for
that
isolated
in which Cl, oxygen
(1)
the minimum energy
or part
of
displaced
system
general
for
with C5
saturated
lactones
of the (4),
is
not
*
Snatzke’s near
rule
(6),
26Onm to chirality
atoms C-CO-O-C are co-planar, chirality,
ring
to the same side
I
effect
a fused
conformation
C2, C3, and C4 are co-planar,
slightly
the atoms C-CO-O-C,
17 March 1972)
publication
as in II,
results
* In dihydrofomannosin (S), ring, C-CO-O-C is planar.
II relating
the sign
in the system as in II,
of
C=C-C=O, is,based
or its
in a negative
the c&unsaturated
enantiomer,
Cotton
where the ene-lactone
1669
8-lactone
on the assumption
and asserts
effect,
With this
is
through
fused
that rule,
n+x* Cotton that
the
right-handed when C4 and/or
C3 and C4 to a cyclobutane
1610
No. 17
C5 are asymmetrically
substituted
are known, the absolute the evidence
II,
It
correct.
configurations
has shown that
conformation,
and the axial
results
that,
for
at these
is based
the purposes
in the system C=C-C=O has the same sense bond is ~10 ’
single suggest
opposite
in I and ~25’
were the exists
for
ring
of
suggests
lactone
those
that
(7,8,9).
fusion.
rule,
also
aS-unsaturated
inverse
co-planar
the rule,
A critical
correct,
although
would seem, on the X-ray of
of the substituents
may be assigned.
are generally
in each,
in II,
orientations
evidence,
the torsion
when each is monocyclic.
angle
Dreiding
If
based
chirality
acid
and left-handed
for
introduced
condition
removed,
in this,
aS-unsaturated ring
co-planarity
to be inChirality
about models
is
through
the sign-chirality
6-lactones.
the central incorrectly
free
from strain
then the sign-chirality indeed,
is, III
(10,ll).
and the
For III,
respectively.
the case steroid
evidence
and the ring
(6)
clearly
lactone
as
atoms
requirements cited
was
relationships
relationships is
C-CO-O-C,
Such X-ray
in C=C-C=O, as in the cases
That this
derivative
of
may be imposed by conformational
is
chirality,
but,
butenolide
chirality
6-lactones.
from the fusidic
(6);
established
the isolated
co-planarity
on the assumption
y-lactones
However,
in aB-unsaturated
or by
but with
the
are the same as
shown by CD data (12),
IV, with
AEON (25Onm) = -9 and,
for
IV,
right-
+8 (12).
0
III Snatzke’s
rule
(6)
In the lactones
with
of
the model
I and II are equivalent.
although
survey
chiralities.
A similar formulated
centres
so obtained
on which the rule
appears
or equatorial
IV
would predict lactones
Cotton
so far
exe-unsaturation
it
effects
discussed,
opposite
in sign
the system C=C-C=O is
is cisoid. A rule
relating
the
to those
observed.
transoid,but in enesign
of the n+n* Cotton
1671
No. 17
effect
to the position
terpenes
has been shown to hold
whether
or not C-CO-O-C is
chirality This
and stereochemistry
describe
that,
for
While applied
between
I and II,
lactone
fused,
is
to assign
an absolute
podolactones
lactones
above,
are that
from the plane
(13).
Molecular
for
equivalent
sign
of part
(6),
as in V.
of C-CO-O, as in I,
V.
sign
lactones. may appropriately
Both assumptions
highly
then the substituent
as
when the further
particularly
as is
effect.
of the rule,
A and B (14) If
that,
to
the n-+x* Cotton
may be misleading
be equatorial
structure,
of
the purposes
at Cl4 in inumakilactones all
of
rule
sesqui-
indicate
endo-unsaturated
for
present
ring,
models
a quadrant
and the
II is
y-lactone
the relationships
in general,
on C5 will
configuration
in a-methylene
which hold
C3 and C4 to a second
A, B, C and D (15),
displaced
of those
a substituent
through
studied
in such compounds,
the assumption
is made that
fusion
C=C-C=O chirality
as stated
to pentenolides,
assumption
Cl4 is
co-planar
ag-unsaturated
the relationship
ring
in most cases
in C=C-C=O are the inverse
suggests
of
and,
when the have been made hence,
probable
at this
in (1,2,3),
centre,
V whether
a-
or 8-,
determinable
is neither
on the
evidence
axial
nor equatorial
cited
(14).
and the absolute
configuration
REFERENCES 1.
A.T.
McPhail
2.
H. Lynton,
3.
Y. Ogihara,
4.
A.McL.
5.
A.T.
and G.A. Sim, J.
Can. J.
Y. Iitaka
Mathieson,
McPhail
Chem., 48,
Sim, J.
(B),
962 (1968).
307 (1970).
and S. Shibata,
Tetrahedron
and G.A.
Chem. Sot.
Acta Cryst.,
Letters, Chem. Sot.
824,
1037 (1968).
81 (1963). (B),
1104 (1968).
here
is not
1672
No. 17
6. G. Snatzke,H. Schwang and P. Welzel in "Some Newer PhysicalMethods in Structural Chemistry,"ed. R. Bonnett and J.G. Davis, United Trade Press, London, 1967, p. 157. G. Snatzke,Angew. Chem. int. Ed., 1, 14 (1968). 7. I.L. Karle and J. Karle, Acta Cryst.,825. 434 (1969). 8. R.D. Gilardi and I.L. Karle. Acta Cryst., 826. 207 (1970). 9. F. MO and B.K. Sivertsen,Acta Cryst., 827, 115 (1971). 10. W.D. Godtfredsen,W. V. Daehne, S. Vangedal.A. Marquet,D. Arigoni and A. Melera, Tetrahedron,3,
3505 (1965).
11. A. Cooper and D.C. Hodgkin,Tetrahedron,24, 909 (1968). 12. R. Bucourt,M. Legrand,M. Vignau, J. Tossier and V. Delaroff,Compt. rend. 257, 2679 (1963). 13. W. StUcklin,T.G. Waddell and T.A. Geissman,Tetrahedron,2&, 2397 (1970). 14. S. I&, M. Kodama, M. Sunagawa,T. Takahashi,H. Imamura and 0. Honda, TetrahedronLetters 2065 (1968). S. Iti, M. Sunagawa and H. Honma, Chem. Comm., 91 (1971). 15. M.N. Galbraith,D.S. Horn, Jenneth M. Sasse and D. Adamson.Chem. Comm.. 170 (1970). M.N. Galbraith,D.S. Horn and Jenneth M. Sasse, Chem. Comm., 1362 (1971).
No.
Letters
17,
pp 1669
- 1672,
1972.
Printed
Pergamon Press.
in Great Britain.
THE n-+x* CD OF aB-UNSATURATEDLACTONES
Division
(Received
Results of
(2,3),
is
about
0.51
plane
as C5.
preserved.
in DK 28 February
from X-ray
the as-unsaturated normally from this
A.F. Beecham of Chemical Physics, CSIRO, P.O. Box 160, Clayton, Victoria, Australia 3168.
structure
g-lactone I,
or its plane
ring,
accepted
analyses
suggest
whether
enantiomer, and the ring
Co-planarity
1972;
of
for
that
isolated
in which Cl, oxygen
(1)
the minimum energy
or part
of
displaced
system
general
for
with C5
saturated
lactones
of the (4),
is
not
*
Snatzke’s near
rule
(6),
26Onm to chirality
atoms C-CO-O-C are co-planar, chirality,
ring
to the same side
I
effect
a fused
conformation
C2, C3, and C4 are co-planar,
slightly
the atoms C-CO-O-C,
17 March 1972)
publication
as in II,
results
* In dihydrofomannosin (S), ring, C-CO-O-C is planar.
II relating
the sign
in the system as in II,
of
C=C-C=O, is,based
or its
in a negative
the c&unsaturated
enantiomer,
Cotton
where the ene-lactone
1669
8-lactone
on the assumption
and asserts
effect,
With this
is
through
fused
that rule,
n+x* Cotton that
the
right-handed when C4 and/or
C3 and C4 to a cyclobutane
1610
No. 17
C5 are asymmetrically
substituted
are known, the absolute the evidence
II,
It
correct.
configurations
has shown that
conformation,
and the axial
results
that,
for
at these
is based
the purposes
in the system C=C-C=O has the same sense bond is ~10 ’
single suggest
opposite
in I and ~25’
were the exists
for
ring
of
suggests
lactone
those
that
(7,8,9).
fusion.
rule,
also
aS-unsaturated
inverse
co-planar
the rule,
A critical
correct,
although
would seem, on the X-ray of
of the substituents
may be assigned.
are generally
in each,
in II,
orientations
evidence,
the torsion
when each is monocyclic.
angle
Dreiding
If
based
chirality
acid
and left-handed
for
introduced
condition
removed,
in this,
aS-unsaturated ring
co-planarity
to be inChirality
about models
is
through
the sign-chirality
6-lactones.
the central incorrectly
free
from strain
then the sign-chirality indeed,
is, III
(10,ll).
and the
For III,
respectively.
the case steroid
evidence
and the ring
(6)
clearly
lactone
as
atoms
requirements cited
was
relationships
relationships is
C-CO-O-C,
Such X-ray
in C=C-C=O, as in the cases
That this
derivative
of
may be imposed by conformational
is
chirality,
but,
butenolide
chirality
6-lactones.
from the fusidic
(6);
established
the isolated
co-planarity
on the assumption
y-lactones
However,
in aB-unsaturated
or by
but with
the
are the same as
shown by CD data (12),
IV, with
AEON (25Onm) = -9 and,
for
IV,
right-
+8 (12).
0
III Snatzke’s
rule
(6)
In the lactones
with
of
the model
I and II are equivalent.
although
survey
chiralities.
A similar formulated
centres
so obtained
on which the rule
appears
or equatorial
IV
would predict lactones
Cotton
so far
exe-unsaturation
it
effects
discussed,
opposite
in sign
the system C=C-C=O is
is cisoid. A rule
relating
the
to those
observed.
transoid,but in enesign
of the n+n* Cotton
1671
No. 17
effect
to the position
terpenes
has been shown to hold
whether
or not C-CO-O-C is
chirality This
and stereochemistry
describe
that,
for
While applied
between
I and II,
lactone
fused,
is
to assign
an absolute
podolactones
lactones
above,
are that
from the plane
(13).
Molecular
for
equivalent
sign
of part
(6),
as in V.
of C-CO-O, as in I,
V.
sign
lactones. may appropriately
Both assumptions
highly
then the substituent
as
when the further
particularly
as is
effect.
of the rule,
A and B (14) If
that,
to
the n-+x* Cotton
may be misleading
be equatorial
structure,
of
the purposes
at Cl4 in inumakilactones all
of
rule
sesqui-
indicate
endo-unsaturated
for
present
ring,
models
a quadrant
and the
II is
y-lactone
the relationships
in general,
on C5 will
configuration
in a-methylene
which hold
C3 and C4 to a second
A, B, C and D (15),
displaced
of those
a substituent
through
studied
in such compounds,
the assumption
is made that
fusion
C=C-C=O chirality
as stated
to pentenolides,
assumption
Cl4 is
co-planar
ag-unsaturated
the relationship
ring
in most cases
in C=C-C=O are the inverse
suggests
of
and,
when the have been made hence,
probable
at this
in (1,2,3),
centre,
V whether
a-
or 8-,
determinable
is neither
on the
evidence
axial
nor equatorial
cited
(14).
and the absolute
configuration
REFERENCES 1.
A.T.
McPhail
2.
H. Lynton,
3.
Y. Ogihara,
4.
A.McL.
5.
A.T.
and G.A. Sim, J.
Can. J.
Y. Iitaka
Mathieson,
McPhail
Chem., 48,
Sim, J.
(B),
962 (1968).
307 (1970).
and S. Shibata,
Tetrahedron
and G.A.
Chem. Sot.
Acta Cryst.,
Letters, Chem. Sot.
824,
1037 (1968).
81 (1963). (B),
1104 (1968).
here
is not
1672
No. 17
6. G. Snatzke,H. Schwang and P. Welzel in "Some Newer PhysicalMethods in Structural Chemistry,"ed. R. Bonnett and J.G. Davis, United Trade Press, London, 1967, p. 157. G. Snatzke,Angew. Chem. int. Ed., 1, 14 (1968). 7. I.L. Karle and J. Karle, Acta Cryst.,825. 434 (1969). 8. R.D. Gilardi and I.L. Karle. Acta Cryst., 826. 207 (1970). 9. F. MO and B.K. Sivertsen,Acta Cryst., 827, 115 (1971). 10. W.D. Godtfredsen,W. V. Daehne, S. Vangedal.A. Marquet,D. Arigoni and A. Melera, Tetrahedron,3,
3505 (1965).
11. A. Cooper and D.C. Hodgkin,Tetrahedron,24, 909 (1968). 12. R. Bucourt,M. Legrand,M. Vignau, J. Tossier and V. Delaroff,Compt. rend. 257, 2679 (1963). 13. W. StUcklin,T.G. Waddell and T.A. Geissman,Tetrahedron,2&, 2397 (1970). 14. S. I&, M. Kodama, M. Sunagawa,T. Takahashi,H. Imamura and 0. Honda, TetrahedronLetters 2065 (1968). S. Iti, M. Sunagawa and H. Honma, Chem. Comm., 91 (1971). 15. M.N. Galbraith,D.S. Horn, Jenneth M. Sasse and D. Adamson.Chem. Comm.. 170 (1970). M.N. Galbraith,D.S. Horn and Jenneth M. Sasse, Chem. Comm., 1362 (1971).