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Model Reaction for the Biosynthesis of the Crinin Alkaloids.

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(2),the acrylonitrile molecule is bound via the nitrogen atom,
and the trigonal bipyramid of the Fe(C0)5 is axially substituted. I n ( 3 ) . the olefinic double bond is coordinated, and
the bipyramid is equatorially substituted.
According to the HSAB concept [31, acrylonitrile is both a soft
and a hard base, depending o n whether the molecule reacts
viu the olefinic double bond or via the free electron pair on the
nitrogen.It should therefore be possible t o distinguish between
a hard and a soft "position" in Fe(CO)5, since hard ligands
always substitute in the axial position 121. X-ray structural
analysis of ( I ) has shown that acrylonitrile is coordinated
both as a hard and as a soft base in this complex. ( I ) contains
by Barton[Z] and verified by isotope experiments 131. On the
basis of this biosynthetic path, we found the ring system ( 5 )
of the crinin alkaloids particularly easy to prepare from a
norbelladin derivative (3).
Zm p
?H
?
H2C-O
HO
i)H
0
r,,
0-c
\ HE-C=N
@
HsCO
a ring system in which both of the iron atoms and both of the
acrylonitrile molecules take part.
Each of the iron atoms is coordinated t o one of the acrylonitrile molecules via the nitrogen atom and t o the other via
the olefinic double bond. The configuration at the iron atoms
is a compromise between a trigonal bipyramid and a tetragonal pyramid. If the configuration is regarded as a distorted
trigonal bipyramid, the olefinic double bonds have replaced
a n equatorial C O group and the nitrogen atoms an axial
C O group, as must be expected from (2) and ( 3 ) .
According t o the existing results, the C E N --f Fe linkage is
not linear. This is understandable if the nitrogen is assumed
to be sp2 hybridized. In free nitriles, the resonance hybrids
( 4 ) and ( 5 ) are present in roughly the same amounts[41, so
that sp2 hybridization may be assumed in ( I ) .
The compound (f) crystallizes in the triclinic system with the
space group Ct-Pl;, with one molecule in the unit cell. The
lattice constants are u = 6.40 A, b = 9.57 A, c = 6.51 A, cc =
93.0 ', p = 106.6 O y = 105.4 '. The structure was determined
by three-dimensional Patterson and Fourier syntheses. The
provisional R value is 20 %.
Received: January 10, 1968
[Z 707 IE]
German version: Angew. Chem. 80, 239 (1968)
[*I Dr. M. L. Ziegler
Anorganisch-Chemisches Institut der Universitat
69 Heidelberg, Tiergartenstr. (Germany)
[l] S. F. A. Kettle and L. E. Orgel, Chem. and Ind. 1960,49.
[2] E. Schubert and R. K . Sheline, Inorg. Chem. 5, 1071 (1966).
131 R. G. Pearson, J. Amer. chem. SOC.85, 3533 (1963).
[4] W . Gerrard, M. F. Lappert, H . Pyszora, and J . W . Wallis, J.
chem. SOC.(London) 1960, 2182.
Model Reaction for the Biosynthesis of the
Crinin A l k a l o i d s [ l l
By B. Franck and H. J . Lubs[*]
Crinin (2) and about thirty similar alkaloids from Amaryllidaceae are formed in the plant cell by oxidative condensation of norbelladin ( I ) , according t o a hypothesis advanced
Angew. Chem. internat. Edit. J Vol. 7 (1968) 1 No. 3
OH
H3C0
OH
(4)
(3)
OR
IS), R = H
(6). R = Ac
Methoxy-0-methylnorbelladin (3) [41 was N-trifluoroacetylated and then oxidized for 48 hours at 20°C in the twophase system CHC13/1N FeC13 (1 :l). Chromatography of the
reaction mixture (ethyl acetate/benzene, 1:1, o n silica gel G)
gave the dienone ( 4 ) in 1 2 % yield. This underwent a second
intramolecular condensation o n hydrolysis with CHCl3/2 N
Na2CO3 (20 "C) t o give the amine (5) C I ~ H ~ ~ m.p.
N O 232~ ,
234 "C (dec.), which takes up 1 mole of H2 on hydrogenation
with HZiPd in CH30H. The structure ( 6 ) is verified for the
monoacetate C19H21N05, m.p. 210 "C, by the following spectroscopic data: IR spectrum in KBr: 1760 (ester), 1695, 1625
cm-1 (enone); N M R spectrum in CDCI3 [TMS = 0): 6 = 2.30
(COCH3), 3.75, 3.88 ( 2 OCH3), 6.47, 6.75, and 6.98 (H on
C-1, 7, 10); mass spectrum at 7 0 eV: m/e = 343 (91 %, Me),
301 (base peak, M-CHz=C=O), 286 (301 - CH3), 272
(301 - CHO), 258 (286 - CO), 227 (258 - CH,).
Received: January 15. 1968
[Z 711 IE]
German version: Angew. Chem. 80, 238 (1968)
[*] Prof. Dr. B. Franck and Dip1.-Chem. H. J. Lubs
Institut fur Organische Chemie der Universitat
23 Kiel, Neue Universitat (Germany)
[I] Part 10 of Alkaloid Syntheses by Oxidative Condensation
under Biogenetic Conditions. - Part 9: B. Franck, G. Dunkelmann, and H . J . Lubs, Angew. Chem. 79, 1066 (1967); Angew.
Chem. internat. Edit. 6, 1075 (1967).
[2] D . H. R. Burfon and T . Cohen: Festschrift A. Stoll. Birkhauser, Basel 1956, p. 117.
[3] D . H. R. Barton, G . W . Kirby, J . B. Taylor, and G . M . Thomas,
Proc. chem. SOC.(London) 1961, 254; J. chem. SOC.(London)
1963, 4545; A . R. Baftersby, H . M . Fales, and W . C. Wildman, J .
Amer. chem. SOC.83, 4098 (1961).
[4] R. A. Abramowitch and S . Takahaski, Chem. and Ind.
1963, 1039; M . Schiebel, Dissertation, Universitat Gottingen,
1965.
22 3
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