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Highly Selective Synthesis of (E)-Alkene Isosteric Dipeptides With High Optical Purity via RCu(CN)Li╖BF3 Mediated Reaction.

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[26] D. Schuld, R. Hoppe. 2. Anorg. A / & . Chem., in press.
C S , N ~ , ~ [ ( G ~ O , ) , ] ,and
[ ' ~ ~mixed chains consisting of tetra[27] R. Hoppe, J. Birx, 2. Anorg. Allg Chem. 557 (1988) 171
hedra and squares in Rb5[0,,,Si0,Li0,Si0,Ni0,,,] .Iz4] A
1281 H.-P. Miiller, R. Hoppe, 2. Anorg. Allg. Chem. 569 (1989) 16.
unique kind of chain is present in K,Be,O,, in which planar
[29] G. Brachtel, R. Hoppe, Nulurwi.ysenschu/ien 64 (1977) 271.
triple coordination and tetrahedral coordination alternate
[30] G . Brachtel, R. Hoppe, Angew. Chem. 8 9 (1977) 45: Angew. Chem. lnt. Ed.
according to the formula ~[0,,2Be[310Be[310,,2Be131];[251Engl. 16 (1977) 43.
1311 R. Hoppe, Angew. Chem. 78 (1966) 52: Angen,. Chem. I n t . Ed. Engl. 5
that is, the "butterfly motif" of oxides such as
(1966) 95; ibid. 82 (1970) 7 and 9 (1970) 25.
K,Na,[O,MOMO,] with M = Be,[261CO>'~]and Fe[281(in
[32] J. Kissel, R. Hoppe. Z . Anorg. AIIg. Chem., in press.
Cs,K,[Fe,O,]) is combined with BeO, tetrahedra. In addition, there are layer structures (Na,[Fe,05][291) and framework structures such as KGaO, .123J
However, chains consisting of rings are rare for such oxides. So far, we have found only one other example,
Na,,[Fe,O,,], in which twelve- and eight-membered rings
Highly Selective Synthesis of (E)-Alkene Isosteric
made up of Fe and 0 alternate.[301{Li,[MnO,],}'o-, conDipeptides With High OpticaI Purity via
sisting of alternating cyclohexane- and cyclooctane-like
RCu(CN)Li BF, Mediated
rings, is much more complicated, since [Mn0,I3- groups are
Reaction **
involved in the structure.
The Madelung Part of Lattice Energy
was
By Toshiro Ibuka,* Hiromu Habashita, Susumu Funakoshi,
calculated and a value of MAPLE(Mn,O,) = 9694 kcdl
Nobutaka Fujii,* Yusaku Oguchi, Tadao Uyehara,
mol-' was obtained. This value is in good agreement
and Yoshinori Yamamoto *
(-0.2%) with the MAPLE values for Mn,O, from the
K , (Li[OMnO,],) structure determinati~n[~I
and for V,O,
The concept of replacing the scissile C-N unit of a peptide
from the orthovanadates(v) (A,LiVO, with A = K, Rb,
bond in enzyme substrates by suitable isosteric units that
C S " . ~and
] Rb,V,0,1321).
could provide potential protease inhibitors has drawn a lot
of attention in recent years."' Thus, it has been suggested
that replacement of the arnide bond (-CO-NH-) of a peptide
Received: January 26, 1990 [Z 3762 IEj
1 by an (E)-double bond might provide "(E)-CH=CH
German version: Angew. Chem. 102 (1990) 835
isosteres" 2 possessing high lipophilicity as well as enhanced
resistance to biodegradation.[']
-
J. Kissel. R. Hoppe, 2. Anorg. Allg. Chem. 750 (1989) 109-118.
J. Kissel, R. Hoppe, 2. Anorg. ANg. Chem. 751 (1989) 113-126.
D. Fischer, R. Hoppe, 2. Anorg. Allg. Chem., in press.
The preparation was carried out by annealing thoroughly mixed amounts
of Na,O, and LiMnO, (Na:Mn =2.8:1) in Ag bombs (SSOT, 30d).
Both the starting materials and the product were handled under dry argon.
[5] Crystal data: Na,,{Li,[MnO,],}
crystallizes orthorhombically, space
group Pnmu (No. 62) with a = 1048.1(7), b = 1518.4(9),c = 1044.4(6) pm
(diffractometer data), 2 = 16, p(MoK.) = 31.4cm-'. 2469 unique reflections (3" I 0 I 30") were measured (Siemens AED 2 four-circle diffractometer with Mo,, radiation, graphite monochromator); absorption correction. The structure was solved by the use of direct methods in
conjunction with difference Fourier syntheses (SHELX-76 and -86)[6].
The subsequent refinement of the parameters, carried out with "anisotropic" temperature factors (least-squares method), gave R = 8.6%, R, =
3.6% ( w = 0.5451 u-, (Fa)for 2450 reflections; goodness of fit = [Xw(F,~'),/(N"~~~""~-N~=
~ ~1.138.
* ~ ~ ,Further
= , ~ ) ] 'details
',
of the crystal structure investigation may be obtained from the Fachinformationszentrum
Karlsruhe, Gesellschaft fur wissenschaftlich-technischeInformation mbH,
D-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository
number CSD-54425, the names of the authors, and the journal citation.
161 G. Sheldrick, SHELX-76 and SHELXS-86 Progrummsysrem, Cambridge
University, England, and Universitdt Gottingen, FRG.
[7] R. Hoppe, Angew. Ckem. 92 (1980) 106; Angew. Chem. I n l . Ed. Engl. 19
(1980) 110.
[8] G. Meyer, R. Hoppe, 2. Anorg. Allg. Chem. 420 (1976) 40.
191 R. Hoppe, %. Kristallogr. 150 (1979) 23.
[lo] H. Rieck, R. Hoppe, 2. Anorg. Allg. Chem. 400 (1973) 311
[ l l ] R. Hoppe. Angew. Chem. 76 (1964) 455; Angew. Ckem. Inr. Ed. EngI. 3
(1964) 532.
[12] R. Baier, R. Hoppe. 2. Anorg. Allg. Chem. 546 (1987) 122.
[13] H.Rieck, R. Hoppe, Nufurwissenschuften 61 (1974) 126.
[14] H.Rieck, R. Hoppe, Angew. Ckem. 85 (1973) 589; Angew. Chem. Inl. Ed.
Engl. 12 (1973) 673.
I151 B. Braze], R. Hoppe, 2. Anorg. Allg. Ckem. 493 (1982) 93.
[16] R. Werthmann, R. Hoppe, 2. Anorg. ANg. Chem. in press.
[I71 R. Wolf, R. Hoppe, 2. Anorg. Allg. Chem. 539 (1985) 39.
[18] B. Burow, R. Hoppe, 2. Anorg. Allg. Chem. 467(1980) 158.
[19] W.Losert, R. Hoppe, 2.Anorg. Allg. Chem. 524 (1985) 7.
[20] H.D. Wasel-Nielen, R. Hoppe, 2. Anorg. Allg. Chem. 359 (1968) 36.
[21] H. Klassen, R. Hoppe, Z. Anorg. Allg. Chem. 497 (1983) 70.
[22] K. Mader, Diplomarbeif, Universitat Giessen 1990.
[23] H:P. Muller, Di.yserlation, Universitat Giessen 1990.
[24] R. Hofmann, R. Hoppe, Z . Anorg. Allg. Chem. S69 (1989) 31
[25] D. Schuld. R. Hoppe, 2. Anorg. Aflg. Chem., in press.
[l]
[2]
[3]
[4]
Angew. Chem. l n t . Ed. Engl. 29 (1990) No. 7
0 VCH
The (E)-CH=CH- bonding in 2 closely resembles the
three-dimensional shape (rigidity, bond angle, and bond
length) of the parent amide l.[,]Except in a few cases,I4I
however, published synthetic routes to such peptide mimics
give unsatisfactory results with regard to double bond geometry and/or stereochemistry at the a-position.IS1For example, the reaction of cr,&unsaturated esters with lithium diisopropylamide (LDA) followed by alkyl halides gave, as one
might expect, both a-alkylation isomers and a dialkylated
by-product.[61Clearly, development of an efficient synthetic
route to compounds of type 2 would be extremely valuable.
We now report another solution, based on the 1,3-chirality
transfer reaction of y-mesyloxy-a,p-enoates, to the problem
of controlling the double bond geometry at the P,y-position
and the stereochemistry of the chiral carbon center at the
a-position. The requisite y-mesyloxy-(E)-a,p-enoates (3, 5,
[*I Associate Prof. Dr. T. Ibuka, Prof. Dr. N. Fujii, H. Habashita, Associate
Prof. Dr. S. Funakoshi
Faculty of Pharmaceutical Sciences, Kyoto University
Kyoto 606 (Japan)
Prof. Dr. Y Yamamoto, Y. Oguchi, Associate Prof. Dr. T. Uyehdra
Department of Chemistry, Faculty of Science, Tohoku University,
Sendai 980 (Japan)
[**I We thank Dr. G. J. Hanson, Department of Medicinal Chemistry, G . D
Searle & Co., Skokie, Ill, USA., for sending us the 'H-NMR spectra of
authentic rert-butyl N-[(IS, 2S)-l-benzyl-2-hydroxy-3-butenylcarbonate
and its (lS, 2R)-isomer. We also thank Dr. P . Herold. Ciba-Geigy AG.
Zentrale Forschungslaboratorien, Basel, Switzerland, for providing us
with the 'H-NMR spectra ofauthentic tert-butyl(4S. 1'S)-4-(l-hydroxy-2propenyI-2,2-dimethyl-1,3-oxazo~idine-3-carboxylate
and its isomer. This
work was supported by the Sound Technology Promotion Foundation.
Verlagsgesellschajt mbH, 0-6940 Weinheim, 1990
0570-0833/90/0707-0801$ 0 3 S0+.25/0
801
16, and 18), (4 and 6), (15), and (17 and 19) for the present
isosteric dipeptide synthesis were readily prepared in acceptable yields from (3-serine, (S)-threonine, (5')-alanine, and
(9-phenylalanine, respectively, according to the usual method.''] Reaction of the rnesylate (3) with MeCu(CN)Li.BF,
(LiBr) in THF/Et,O (ca. l5/l), iso-BuCu(CN)Li.BF, in
THF, and PhCH,Cu(CN)Li.BF, in THF/cyclohexane (ca.
5jl) at - 78 "C for 30 min gave the regio-, (E)-stereo-, and
diastereoselective 1,3-chirality transfer products 7 (98 %
yield), 8 (97% yield), and 9 (97% yield), respectively, after
flash chromatography over silica gel (Table 1, entries 1, 2,
and 3). In a similar manner, other substrates 4-6 and 15- 19)
gave the desired products in acceptable chemical and optical
yields by treatment with organocyanocopper as shown in
OMS
o+co2MeH i
+
R'
R'
- kN
0
C02Me
'Boc
*N,BOC
7 R'=H;
3 R=H
4 R=Me
11
OMS
R-CO2Me
HNBoc
18 R=OTBS
19 R = P h
R'=W
C02Me
_t
-
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
3
3
3
4
5
5
5
6
15
16
16
17
17
18
18
19
Reagent [b]
MeCu(CN)Li. BF,(LiBr)
iso-BuCu(CN)Li . BF,
PhCH,Cu(CN)Li . BF,
MeCu(CN)Li . BF,(LiBr)
MeCu(CN)Li. BF,(LiBr)
iso-BuCu(CN)Li. BF,
PhCH,Cu(CN)Li. BF,
MeCu(CN)Li . BF,(LiBr)
MeCu(CN)Li . BF,(LiBr)
MeCu(CN)Li . BF,(LiBr)
iso-BuCu(CN)Li. BF,
MeCu(CN)Li. BF,(LiBr)
iso-BuCu(CN)Li . BF,
MeCu(CN)Li. BF,(LiBr)
iso-BuCu(CN)Li. BF,
MeCu(CN)Li. BF,(LiBr)
iso-BuCu(CN)Li . BF,
19
HNBoc
R'=H;
R' =OTBS;
R' = OTBS:
R'=Ph;
R'=Ph;
R2=Me
R;=M
R. = iBu
RZ=Me
R2=iBu
R2
R' +C02Me
HNBoc
25 R'=OTBS;
26 R'=OTBS;
27 R'=Ph;
28 R'=Ph;
R2=Me
2
R =tBu
2
R2=Me
R =/Bu
7
8
98% (>99:1)
97% (>99:1)
97% (>99:1)
79% (>95:5)
94% (>97:3)
97% (>97:3)
73% (>85:15)
80% (>94:6)
93% (>99:1)
92% ( > 9 9 . 1 )
93% (>99:1)
96% (>99:1)
97% (>99:1)
91 % (>97:3)
94% (>97:3)
98% (>99.1)
96% (>99:1)
9
10
11
12
13
14
20
21
22
23
24
25
26
27
28
tion within a few minutes, although the reaction mixture was
stirred for 30 min. Furthermore, the geometry of the fi,y
double bond of the products (7-14 and 20-28) is exclusively
the desired geometry ( E ) and the diastereoselectivity is in the
range of 97:3 to >99: 1-xcept
in the case of entries 4, 7,
and 8. The presence of an HNBoc group at the &position in
the substrates (15-19) does not exert any influence on the
course of the anti-SJ reaction.
The absolute configuration of the alkyl-bearing carbon
center, although apparent from the reaction course of the
anti-SJ attack of the organocopper reagents['-lO."a.
and from the E-geometry of the P,y-double bond of the products, could be established by chemical degradation. For example, ozonolysis of benzyl ether 29 and 31, derived from 7
and 20 by a two-step reaction (1. diisobutylaluminum hydride, room temperature (DIBAL) in CH,CI,, -78 "C;
2. NaH/BnBr in DMF, 0 "C room temperature), followed
by reduction with DIBAL, gave the known alcohols 30,
-
Scheme 1. Abbreviations: OMS = methanesulfonyloxy; OTBS = rert-butyldimethylsilyloxy; Boc = /err-butoxycarbonyl.
Me
- ok
Me
-0Bn
Scheme 1 and Table 1 . The diastereoselectivities shown in
Table 1 were determined by 'H NMR in CDCI, for isolated
comDounds: >99: 1 indicates that the other diastereomer
was -not detectable. Additionally, in some cases (Table 1,
entries 1,4, 11, 14), diastereoselectivities were determined by
capillary gas-chromatography (50 m x 0.2 mm).
To achieve very high chemical and optical yields, it should
be noted that a y-mesyloxy group in the substrate,
organocyanocopper . BF, reagent, and T H F or a mixed solvent involving THF are essential.['] Addition of BF, . Et,O
is essential for the clean 1,3-chirality transfer.''] The reactions with organocyanocopper . BF, reagents in a solvent
involving T H F were very fast at -78 "C and went to comple802
Isolated yield [YO]
(Diastereoselectivity at C-Z)[c]
Product
R2=W
R2
..
20
21
22
23
24
SubStrate
~
12 R'=H; R2=iBu
13 R'=H; R2=CH2Ph
14 R' =Me; R'= Me
OMS
R +C02Me
HNBoc
15 R = H
16 R = OTBS
17 R = P h
R'=H;
Entry
[a] All reactions were carried out at - 78 "C for 30 min with 3-4 molar equiv.
of reagents. [b] The notation MeCu(CN)Li. BF,(LiBr) is intended to indicate
that the reagent has been prepared from ethereal MeLi as the LiBr complex (see,
Ref. [Sc] and [Ed]) Substrates 4 and 6 gave comparable results on treatment
with MeCu(CN)Li .BF,(LiI) as for the entries 4 and 8. [c] All the new compounds have been fully characterized spectrally [IR(CHCl,), 'H-NMR
(CDCI,) and CD (isooctane)] and their elemental compositions have been determined by high-resolution mass spectroscopy and/or combustion analysis.
Diastereoselectivities were determined by 'H NMR (200, 270, 300, and/or
400 MHz).
8 R'=H;
R2=iBu
9 R'=H;
R2' = C H ~ P ~
10 R'=Me; R =Me
5 R=H
6 R=Me
Table 1. Synthesis of protected (E)-CH = CH isosteres by reaction of 6-N-Bocamino-y-mesyloxy-(E)-a,p-enoates
with organocyanocopper-boron trifluoride
reagents.[a]
0 VCH Verlagsgesellschafi mbH. 0-6940
Weinheim, 1990
/
+
C02Me
N BOC
O~NBOC
29
7
Me
H
-
Me
C02Me
HNBoc
-
20
H
Me
Me =,=
Y O B n _ _ ,
BnNBoc
31
Me
HOJ-OB~
30
Me
HO-OBn
32
[c(]iz
= +17.2 (CHCI,), and 32, [a]io= -17.2'
(CHCI,).
The optical rotations of 30 and 32 exactly match the reported
'1
0570-0833f90f0707-0802 S 03.50f .25f0
Angew. Chem. In[. Ed. Engl. 29 (1990) No. 7
Although all of the controlling factors in the present
organocyanocopper.BF,-mediated reaction of 8-tert-butoxycarbonylamino-y-mesyloxy-cr,fbenoatesare not clear,
the following explanation concerning the anti-S,2’ reaction
could be drawn. Conformer 15A, which would lead to the
(Z)-olefin, would be destabilized in comparison with 15B
owing to unfavorable interaction between the bulky R group
and the hydrogen. Consequently, elimination of the leaving
group (OMS group) will take place only when the attacking
copper reagent and the leaving group are in a mutual antiperiplanar disposition.
OMS
OMs
Me
C0,Me
HNBoc
15
Me
MeF C 0 , M e
HNBoc
20
-
H
15A
-
1‘
OMS
[Me&L.]
15B
It is apparent from these preliminary data that by judicious selection of organocopper-Lewis acid reagents, the described method offers facile entry to stereochemically pure
isosteric dipeptides.
[3] M. M. Hann, P. G. Sammes, P. D. Kennewell, J. B. Taylor, J Chem. SOC.
Chem. Commun. 1980, 234.
[4] a) A. Spaltenstein, P. A. Carpino, F. Miyake, P. B. Hopkins, J Org. Chem.
52(1987) 3759: b) L. S. Lehman de Gaeta, M. Czarniecki, A. Spakenstem,
ibid. 54 (1989) 4004.
[5] Y-K. Shue, G. M. Camera, A. M. Nadzan, Tetrahedron Lett. 28 (1987)
3225.
[6] N. J. Miles, P. G. Sammes. P. D. Kennewell, R. Westwood. J. Chem. Sac.
Perkin Trans. 11985, 2299.
[7] The syntheses of the homochiral substrates will be reported in the near
future. 17 and 19 were synthesized by the method of Hanson: G. J. Hanson,
T. Lindberg, J Org. Chem. 50 (1985) 5399.
[8] a) T. Ibuka, T. Nakao, S. Nishii, Y Yamamoto, J Am. Chrm. Sac. 108
(1986) 7420: b) T. Ibuka, M. Tanaka, S. Nishii, Y Yamamoto, J Chem.
Sac. Chem. Commun. 1987,1596; c) T. Ibuka, N. Akimoto, M. Tanaka, S.
Nishii, Y. Yamamoto, J. Org. Chem. 54 (1989) 4055; d)T. Ibuka M.
Tanaka, S. Nishii, Y Yamamoto, J. Am. Chem. Soc. If1 (1989) 4864; e) T.
Ibuka, M. Tanaka, Y. Yamamoto, J. Chem. Sac. Chem. Commun. 1989.
967; f ) Y Yamamoto, Angew. Chem. 98 (1986) 945, Angew. Chem. Int. Ed.
En@. 25 (1986) 947: g) C. Girard, I. Romain, M. Ahmar. R. Bloch, Tetrahedron Lett. 30 (1989) 7399.
[9] Nearly all known organocopper reactions with allylic halides, acetates,
and their congeners proceed via anti-S,Z’ displacement. For excellent reviews on S,2’ reactions, see: J. A. Marshall, Chem. Rev. 89 (1989) 1503;
R. M. Magid, Tetrahedron 36 (1980) 1901; for anti-S,Z’ reactions, see:
B. M. Trost, T. P. Klun, J. Org. Chem. 45 (1980) 4256, E. J. Corey. N. W.
Boaz, Tetrahedron Lett. 25 (1984) 3063; I. Fleming, D. Higgins, ibrd. 30
(1989) 5779, and references cited therein.
[lo] For syn-SJ reactions with organocopper reagents, see: J. A. Marshall.
V. H. Audia, J. Org. Chem. 52 (1987) 1106: see also, J. P. Marino, R.
Fernandez de la Pradilla, E. Laborde, rbrd. 52 (1987) 4898.
Ill] a) J. A. Marshall, J. D. Trometer, D. J. Cleary, Tetrahedron 45 (1989) 391
and references cited therein; b) J. A. Marshall, B. E. Blough, J Org. Chem.
55 (1990) 1540: c) H. Nagaoka, Y Kishi. Tetrahedron 37 (1981) 3873.
Experimental
Synthesis of ( E- C H = CH isosteric dipeptides, for example 23: To a stirred
slurry of CuCN (72 mg, 0.8 mmol) in 5 mL of dry THF at -78 “C was added
by syringe 0.533 mL (0.8 mmol) of 1.5 M MeLiILiBr in Et,O: the mixture was
allowed to warm to -20°C and was stirred at this temperature for 10min.
BF, . Et,O (0.1 mL, 0.8 mmol) was added to the above mixture at - 78 “C and
the mixture was stirred for 5 min. A solution of y-mesyloxy-a,P-enoate
(17)(85 mg. 0.2 mmol) in dry T HF (4mL) was added dropwise to the above
reagent at - 78 C with stirring, and stirring was continued for 30 min followed
by quenching with 3 mL of a 2.1 saturated NH,CI-28% NH,OH solution.
The mixture was then extracted with Et,O and the extract was washed successively with 5 % citric acid, 5% NaHCO,, and water, and dried over MgSO,.
Concentration under reduced pressure gave a crystalline residue, which was
purified by flash chromatography over silica gel (n-hexanelEtOAc (411)) followed by recrystallization from n-hexane/Et,O (411) gave the title compound 23
(66 mg, 96% yield) as colorless crystals.-m.p.
74°C; [ff]ko = 36.36
( c = 0.902. CHCI,); IR (CHCI,) cm-’ = 3460, 3010, 2960, 1727 (shoulder).
1713,1498.1459.1440,1372,1174,974;’H-NMR(300MHz,CDC1,):6
= 1.19
(d, J = 7.08 Hz, 3 H), 1.40 (s, 9H), 1.63(broads, 1 H), 2.75-2.89 (m, 2H), 3.11
(m, IH). 3.66 (s, 3H), 4.30-4.50 (m, 2H), 5.49 ( d d , J = 15.22, 4.42 Hz, 1 H),
5.57 (dd, J = 15.22, 6.83 Hz, 1 H), 7.14-7.30 (m, 5H); I3C NMR (75 MHz,
CDCI,): d = 17.21, 28.35, 41.76, 42.45, 51.85, 126.46, 128.28, 129.55, 129.66.
131.43, 137.34, 155.11, 174.89. Satisfactory elemental analysis (C, H, N).
+
Gas-Phase Thermolysis of 6-C yclopropyland 6-Oxiranylpentafulvenes:Novel Routes
to Dihydroindenes and Vinylcyclopentadienes **
By Axel G . Grimbeck,* Karl Peters, Eva-Maria Peters,
and Hans Georg von Schnering
The electrocyclic ring closure of 6-vinylpentafulvenes 1
via gas-phase thermolysis is an efficient and flexible route to
1,5-dihydropentaIenes 2.I” We have now investigated the
[n6 + 02]variant, which should open up a route to the homologous dihydroindenes and oxa analogues thereof.
Received: March 8, 1990 [Z 3842 IE]
German version: Angew. Chem. !02 (1990) 816
111 a) A. Spatola in B. Weinstein (Ed.): Chemistry and Biochemisrry of Amino
Acids. Peptides and Proteins. Val. 7, Marcel Dekker, New York 1983,
p. 267: b) R. L. Johnson, J Med. Chem. 27(1984) 1351: c) Nomenclature,
see: IUPAC-IUB Joint Commission on Biochemical Nomenclature, Eur. J
Biochem. 138(1984) 9: c) For syntheses of non-proteinogenic amino acids,
see: M. T. Reetz, D. Rohrig, Angew. Chem. !Of (1989) 1732; Angew. Chem.
Int. Ed. Engl. 28 (1989) 1706, and references cited therein.
[2] Incorporation of CH =CH isosteres into peptides, see: a) M. T. Cox, J. J.
Gormley, C. F. Hayward, N. N. Petter, J. Chem. Sac. Chem. Commun.
1980, 800; b) G. Precigoux, E. Ouvrard, S. Geoffre, in C. M. Deber, V. J.
Hruby, K. D Kopple (Ed.): Peptides: Structure and Function, Pierce,
Rockford, IL, USA, 1985, p. 763: c) J. S. Kaltenbronn, J. P. Hudspeth,
E. A Lunney, B. M. Michinewicz, E. D. Nicolaides, J. T. Repine, W. H.
Roark. M. A. Stier, E J. Tinney, P. K. W. Woo, A. D. Essenhurg, J. Med.
Chem. 33 (1990) 838.
Angew. Chrm. Int. Ed. Engl. 29 (1990) No. 7
0 VCH
1
2
Both series of compounds are of importance for the synthesis of terpenoid natural produ~ts.[~l
The employment of
6-oxiranylfulvenes in the synthesis of natural products has
already been reported: FuZZis et al.I4]were able to prepare a
[*] Dr. A. G. Griesbeck
Institut fur Organische Chemie
Am Hubland, D-8700 Wurzburg (FRG)
Dr. K. Peters, E.-M. Peters, Prof. Dr. H. G. von Schnering
Max-Planck-Institut fur Festkorperforschung
Heisenbergstrasse 1, D-7000 Stuttgart 80 (FRG)
[**I A . G G . thanks the Fonds der Chemrschen Industrie for a Liebig-Stipendium
Verlagsgesellschaft mbH, 0-6940 Weinheim, 1990
0570-0833/90/0707-0803$03.50+ ,2510
803
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