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Graphical Abstract (Angew. Chem. Int. Ed. Engl. 41995)

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A Journal of t h e
Gesellschaft
Deutscher Chemiker
International Edition in English
1995
34
i
i
369 502
Pages
-
COVER PICTURE
The cover picture shows the space-filling model of an inorganic crown ether compound with an encapsulated sodium ion. The crown consists of six Fe"' ions (virtually hidden) and the 0 atoms (orange) of six p-Me0 ligands (carbon atoms depicted
in white). The Fe centers form an almost regular hexagon; their coordination
spheres are completed by six additional bridging M e 0 ligands, which are also coordinated to the Na ion (yellow), and by six chelating dibenzoylmethanido ligands.
More about this complex ion, which is interesting inter alia with regard to the course
of the hydrolysis of iron(n1) salts and the synthesis of models for the mineral core in
ferritin, is reported by S. J. Lippard et al. on pages 467 ff.
REVIEWS
Contents
To discover how the complex molecule vitamin B,, (shown on the right) was formed
in living systems was one of the greatest challenges in bioorganic chemistry. Since its
structure determination and total synthesis, vitamin B,, has held a special fascination for chemists. But the tremendous achievement chronicled here is also of broader
interest as an example of the productive interplay of modern methods in biology and
chemistry.
Enzymes, a tool of the preparative chemist. The use in synthesis of enzymes such as
the aldolases covered here can no longer be overlooked, particularly in the field of
carbohydrate chemistry. Since, for instance, the saccharides that are found on the
surface of cells are information carriers on the molecular level and play a significant
role in intercellular communication as well as the processes involved in infection,
these processes can only be deliberately influenced if the relevant carbohydrates and
carbohydrate analogs can be prepared stereoselectively in good yields and in sufficient quantities for pharmaceutical applications. Enzymatic syntheses fulfill these
criteria in an elegant way.
Angew. Chem. Int. Ed. Engi. 1995. 34, No. 4
0 VCH
VerIagsgeselkchaf( mhH, 0-69451 Weinherm, 1995
F. Blanche, B. Cameron, J. Crouzet,
L. Debussche, D. Thibaut,
M. Vuilhorgne, F. J. Leeper,
A. R. Battersby * ........................
383-41 1
Vitamin B L 2 : How the Problem of Its
Biosynthesis Was Solved
C.-H. Wong,* R. L. Halcomb,
Y. Ichikawa, T. Kajimoto .......... 412-432
Enzymes in Organic Synthesis: Application
to the Problems of Carbohydrate
Recognition (Part 1)
05704833/95j0404-0371$10.00+.2510
371
HIGHLIGHTS
Contents
The self-assembly of enolates can be controlled by the addition of nonstoichiometric
amounts of metal salts. New findings on the structure-reactivity relationship of
enolates and chemo-, regio-, and diasteroselectivities in their reactions with electrophiles are discussed. This article was prompted by a recent report by Myers et al.
on a new method for the alkylation of amide enolates with pseudoephedrine as a
chiral auxiliary [Eq. (a)].
ph<,kR
K. Ruck* ...................................
433--435
Asymmetric Alkylation of Amide Enolates
with Pseudoephedrine and Ephedrine as
Chiral Auxiliaries-Unexpected Influence
of Additives?
1. 2LDA
6LiQ
OH
Me
2.
OH
R’X
Me
R’
R = Me,Bn,Ph, Q. n-Bu
R’X = MeI, Erl, n-BuI, BnBr
Following the early successes of the di- and trimerization of 1 to give 2 and 3,
R. Streubel* ..............................
436-438
respectively, the tetraphosphabarrelene 4 and the hexapho~pha-p-[3*,5~]octahedrane 5 were synthesized recently. These and other more recent advancements in
Phosphaalkyne Cyclooligomers: From
the field of P-C cage compounds demonstrate once again the synthetic potential of
Dimers to Hexamers-First Steps on the
tert-butylphosphaacetylene, which was prepared for the first time by Becker et al. in
Way to Phosphorus-Carbon Cage Com1981.
pounds
3
2
1
4
5
COMMUNICATIONS
Because of the extraordinary electronic situation in tris(dimethy1amino)cyclopropenylium chloride 1, a salt with an electron-rich cation and anion, the “naked”
C1- ions in 1 show a very high readiness to coordinate to acceptors. Thus, stable
adducts with hydrogen bonds are formed from 1 and carboxylic acids or phenol
derivatives .
R. Weiss,* T. Brenner, F. Hampel,
A. Wolski ...................................
439-441
A hypervalent, one-dimensional polymer with interlocking zigzag chains (shown on the right) is obtained in the reaction of diiodoacetylene with
tris(dimethy1amino)cyclopropenylium iodide. The
formation of the first stable 1:1 adduct from I- ions
and a compound with C,,-bonded I centers is attributed to strong n -+ CT* interactions,
R. Weiss,* M. Rechinger, F. Hampel,
441 -443
A. Wolski ...................................
By conversion of the sulfonium salt 1 with the cyclopentadiene 2 the readily soluble salt
3 is obtained in high yield. “Naked” Cp- ions and cations of [{(Me,N),S},Cp]+
with an inverse sandwich structure are present in crystals of 3. A variety of silylated
N-heterocycles react with 1 in a similar way to form the corresponding salts. These
salts are interesting inter alia for their potential use as building blocks in synthesis.
J. Wessel, U. Behrens, E. Lork,
R. Mews* ..................................
[(Me,N),S]+ [Me,SiFJ
1
312
+
D S i M e ,
2
0 VCH
--+
The Consequences of an Electrostatic
“Forced Marriage” between Two ElectronRich Particles: Strained Ion Pairs
Stable 1 :1 Adducts from Todoacetylenes
and Iodide Ions: Ion Pair Strain as an
Additional Driving Force?
[(Me,N),S]+ [ o ] L 2 M e 3 S i F
3
Verlagsgeseilsrhafi mbH, 0-69451 Weiriheim, 1995
(a)
443-446
Tris(dimethy1amino)sulfoniumcyclopentadienide [TAS] [C,H,] - and Tris(dimethy1amino)sulfoniumpyrrolide
[TAS]+[C4H,NJI-: Two Isostructural Salts
with “Naked” Anions A- and the “Inverse”
Sandwich-Cations [{(Me,N),S),A]+
(A = C,H,-, C,H,N-)
OS70-0833J95JO404-0372
$10.00+ ,2510
+
Angew. Chem. I n ! . Ed. Engl. 1995, 34, No. 4
Con tents
F. Wiirthner, J. Rebek, Jr.* ........ 446-448
Catalysis by flicking a "light switch" is possible with
an azobenzene-based template. When the E isomer
of the template is irradiated with light of wavelength
366 nm. the isomeric composition is shifted in favor
of the catalytically active Z isomer, and the reaction
rate for amide bond formation between modified
adenine units is increased by a factor of 10. The
light-induced activation of the template is depicted
schematically on the right.
Light-Switchable Catalysis in Synthetic
Receptors
The steric demand of an oxygen atom is less than that of a CH, group in the kinetic
resolution of chiral dienophiles with the enantiomerically pure dienes 1 and ent-1
(R = OCH,). This realization led to the first differentiation between enantiotopic
double bonds in a Diels-Alder reaction for the spirolactone 2 and spiroether 3.
B
rip
2
1
P. G. Jones, H. Weinmann,
E. Winterfeldt* ..........................
448-450
Discrimination between Enantiotopic
Groups in a Diels-Alder Reaction
8
3
Structural features of the heavier and lighter homologues of tellurium are embodied in the two partial
structures of Cs,Te,, : crown-shaped Te, rings,
which are stabilized in the coordination sphere of a
cesium cation (shown on the right), are similar to
analogous S, and Se, rings, whereas the layer anions
;[Te,Te:,]
may be derived from the a-polonium
structure. Cs,Te,, was prepared from Cs,CO, and
As,Te, in superheated methanol.
Te
W. S. Sheldrick,*
M. Wachhold .............................
450-451
Discrete Crown-Shaped Te, Rings in
cs3Te22
Te
Despite strong repulsion between the methyl groups, the intramolecular Heck reaction
of cyclohexenyl trifluoromethanesulfonate 1, available from 5-a-cholestan-3-one,
proceeds in 50% yield. The product of the Heck reaction can be converted in a few
subsequent steps into the cholesterol-baccatinIII hybrid 2.
J. J. Masters,* D. K. Jung,
S. J. Danishefsky,* L. B. Snyder,
T. K. Park, R. C. A. Isaacs,
C. A. Alaimo, W. B. Young ....... 452-455
A Novel Intramolecular Heck Reaction:
Synthesis of a Cholesterol-BaccatinIII
Hybrid
0
2
1
The N-silylated chiral amines TMS-SAMP and TMS-RAMP can be employed for
stereoselective C-N bond formation with enantiomeric excesses of 90-98 YO.In
these reactions, the corresponding hydrazinoesters are formed initially, which are
subsequently cleaved hydrogenolytically to give the desired p-amino acids 1. R =
alkyl, R = Me, tBu.
0
a
°
N
C
H
I
3
nBuLil ~
0
0
e-4
455-457
Enantioselective Synthesis of 8-Amino
Acids: TMS-SAMP as a Chiral Ammonia
Equivalent for the Aza Analogous Michael
Addition to a,fi-Unsaturated Esters
R=OH
H",SiMe3
TMS-SAMP
Angebt . Chem. I n t . Ed. Engl. 1995, 34, No. 4
~
D. Enders,* H. Wahl,
W. Bettray ..................................
1
8
VCH Verlagsgesellschafl mbH. 0-69451 Weinheim. 1995
0570-0833/95/0404-0373$ IO.OO+ .ZSiO
373
Contents
lkansmission electron microscopy has been used to characterize the large solvent-stabilized palladium clusters with uniform size distribution that are formed in homogeneous Pd”-catalyzed oxidations in dimethyl sulfoxide.
R. A. T. M. van Benthem, H. Hiemstra,*
P. W. N. M. van Leeuwen, J. W. Geus,
W N. Speckamp ........................
457-460
Sulfoxide-Stabilized Giant Palladium Clusters in Catalyzed Oxidations
A high synthetic potential is promised by imido(imino)phosphorane 2 accessible by
N, elimination from the azidophosphane 1. In 2, as in the isoelectronic oxygen
derivative 3, the phosphorus atom is in a trigonal-planar environment. Ar = 2,4,6tBu,C,H,.
Ar N3
\I
FH
A
P-N(H)Ar
--&
- N2
&-\
“-Ar
3
2
1
Synthesis, Structure, and Reactivity of an
Imido- and an Oxo(imido)phosphorane
R-P(=X)=NR (X = NH, 0;R =
tBu3C6H2)
H0
Ar-P
N-Ar
M. Larbig, M. Nieger,
V. von der Gonna, A. V. Ruban,
E. Niecke* .................................
460-462
Enantiomeric excesses up to 96% have been obtained in allylic alkylations of 3-aryl2-propenyl phosphates 2 to give 3 with CH(C0,Me); as nucleophile Nu- by using
a new tungsten catalyst derived from the phosphanodihydrooxazole complex 1
(X = CH3CN). The regioselectivity is opposite to that of analogous Pd-catalyzed
reactions.
G. C. Lloyd-Jones,
A. Pfaltz* ..................................
462-464
Chiral Phosphanodihydrooxazoles
in
Asymmetric Catalysis : Tungsten-Catalyzed
Allylic Substitution
0
2
3
06-96%W
Indigo in which =O is replaced by =C(CN), (1) or =N-CN was prepared for the
first time. Both compounds and their derivatives absorb in the near-IR at considerably longer wavelengths than indigo. Attempts to synthesize the analogous
thioindigo derivatives led to compounds 2-4 (X = S, SO,) by reaction sequences
that were sometimes unexpected.
R. Gompper,* K. Hartmann,
R. Kellner, K. Polborn .............. 464-467
Bis(dicyanomethy1ene) and Bis(cyanoimino) Derivatives of Indigo and Thioindigo
NC
k C N
\
HNC
1
‘
CN
S
S
2
’
3
A crown composed purely of inorganic components forms the core of complex cation
1. Interest in this polyiron ion is based on its potential relevance to intermediates in
the formation of the ferritin core and the hydrolytic polymerization of Fe”’ salts. The
crown structure is supported by the inclusion of a sodium ion within the Fe,O, ring.
[NaFe,(OCH,),,(dbm),]+
1, Hdbm = dibenzoylmethane
Fast exchange with surrounding water protons need
not attenuate ‘H NMR signals of proteins in solution. A modified pulse sequence has been developed
to increase the signal intensity of the amide protons;
on the right the improvement in sensitivity (a +c) is
shown for a selected residue in a protein. This new
technique should aid elucidation of protein structures in solution.
A. Caneschi, A. Cornia,
S. J. Lippard* ............................
467-469
A Cyclic Hexairon(I1r) Complex with an
Octahedrally Coordinated Sodium Ion
at the Center, an Example of the
[12]Metallacrown-6 Structure Type
W. Jahnke, H. Kessler* ............. 469-471
Modified Triple Resonance NMR Experiments with Optimized Sensitivity for
Rapidly Exchanging Protons
I
,
,
8.0
b (’H)
374
0 VCH
Verlagsgesellschaft mbH. D-694Sf Weinheim. !99S
OS70-0833/9Sj0404-0374 $10.00+ .2S/O
Angew. Chem. Int. Ed. Engl. 1995. 34, No. 4
By combination of an Arndt-Eistert reaction sequence and a peptide coupling, amino
acids and peptides can be coupled with a second amino acid or a second peptide to
give homopeptides, for example of type 1. This method has been employed to
synthesize up to homohexapeptides.
R'
R3
--
J. Podlech, D. Seebach* ............. 471 -472
The Arndt-Eistert Reaction in Peptide
Chemistry: A Facile Access to Homopeptides
__c
The methyl groups in copper complex 1 not only prevent dimerization but also activate the complex for
RNA hydrolysis. The half-life for the hydrolysis of
ApA (0.5 mM) promoted by 1 is only 3 min. Thus 1
is currently the most effective transition metal complex for hydrolyzing RNA.
CH3
B. Linkletter, J. Chin* ............... 472-474
b i d Hydrolysis of RNA with a Cu" Com-
CH3
1
Macrocycles of type 2 with up to 26 ring atoms (n = 22) are available in very good
yields by photo electron transfer (PET) initiated decarboxylation of the anions of
N-phthaloyl-o-aminocarboxylicacids 1. The electron transfer is favored as a result
of intramolecular K +-mediated chelation; however, it can also occur efficiently over
larger donor-acceDtor distances.
1 n = 1,2,3,9,22
A. G. Griesbeck,* A. Henz,
K. Peters, E.-M. Peters,
H. G. von Schnering .................. 474-476
Photo Electron Transfer Induced Macrocyclization of N-Phthaloyl-w-aminocarboxylic Acids
2 (8049%)
When the copper center is stabilized by donor ligands such as H,O and NH,, trialkylcopper compounds correspond to energy minima at all levels of theory used in the
calculations (MP2, SCRF, BLYP). These results support proposals that such species
are intermediates in cuprate addition and substitution reactions and at the same time
suggest that descriptions of trialkylcopper systems as Cu" rather than Cu"' complexes may be more appropriate.
A. E. Dorigo, J. Wanner,
P. vonR. Schleyer* ....................
A four-membered ring of two lithium and two nitrogen atoms is in the central unit of
the dimer in the title (l),a complex between an alkali metal and a neutral phosphorus ylide. Surprisingly, this is the first time that such a model complex for the
generation of ylides from phosphonium salts and alkali metal bases has been characterized in the solid state. The structure in solution was also determined, and the
complexation energies for this and other model complexes were estimated by ab
initio calculations.
D. R. Armstrong, M. G. Davidson,*
478-481
D. Moncrieff ..............................
[(PhCH,),NLi CH2PPh,],
1
stitution Reactions with Dialkylcuprates
The First Unambiguous Characterization
of a Neutral Phosphorus Ylide-Lithium
Complex: Isolation, Structure, and Ab
Initio Investigations of [(PhCH,),NLi.
CH,PPh,l*
C,,H6, and C,,H,,: Silver Ion Extraction
with New Concave Hydrocarbons
1
Ckem.Inr. Ed. Engl. 1995. 34, No. 4
Computational Evidence for the Existence
of Cu"' Intermediates in Addition and Sub-
J. Gross, G. Harder, F. Vogtle,*
H. Stephan, K. Gloe .................. 481-484
The intramolecular cavity of the spherical, concave
hydrocarbons C60H601 and C,,H,, 2 is accessible
to guest molecules through openings on their surfaces. The new carbocycles can be used to extract
silver ions from the aqueous phase; 1 shows high
selectivity and the best extraction properties of the
known complex-forming hydrocarbons.
Angew.
476-478
0 VCH Verlagsgesellsckaft mbH, 0-69451
2
Weinkeim,1995
0570-0833/95/0404-0375 $10.00+ ,2510
375
Contents
Two new tetrameric phosphaalkynes,the isomers 1 and 3, have been synthesized. The
cyclotetramer 1 with a “central” P4 unit forms in high yield by the demetalation of
the zirconium compound 2 with [(Ph,P),NiCl,]. The isomer 3, which contains two
P-C double bonds, is obtained as a by-product in the reaction of 2 with hexachloroethane; the major product is the tetraphosphacubane 4.
t Bu
tBu
1
tBu
)rF:
tBu
P A t B U
1
3
2
B. Geissler, S. Barth, U. Bergstrasser,
M. Slany, J. Durkin, P. B. Hitchcock,
M. Hofmann, P. Binger,*
J. F. Nixon,* P. von R. Schleyer,*
484-487
M. Reg&* ................................
Tetraphosphatricyclo[4.2.0.02~
’loctadienes; New Phosphaalkyne Cyclotetramers Derived from h302-Diphosphetes
4
For the first time the carbene character of a formyl anion equivalent can be demonstrated in the crystal structure of the title compound 1. A comparison of the structures of thiazole, the stable nucleophilic carbene 2 (both accessible experimentally),
and LiCH=O (calculated) leads to this result. Furthermore, 1 is yet another example
of complexes of nucleophilic carbenes with Lewis acids, which have aroused great
interest lately.
a;H
G. Boche,* C. Hilf, K. Harms,
M. Marsch, J. C. W. Lohrenz ..... 487-489
Crystal Structure of the Dimeric (4-lertButylthiazolato)(glyme)lithium: Carbene
Character of a Formyl Anion Equivalent
As long as an enthalpic barrier is
X
X
present, a decrease in the electron-releasing ability of X and Y causes an
(a)
increase in the reaction rates of reaction (a) due to the lowering of the
Y
Y
activation enthalpy, while the activation entropy remains constant.
When the enthalpic barrier disappears, further decrease in the electron-releasing
ability of X and Y is associated with an increase in reactivity caused by an increase
in the activation entropy.
M. Patz, H. Mayr,* J. Bartl,
S. Steenken ................................
A L3,a2Sb-C double bond that is not part of a cyclic
electron system is present in the distibabutadiene 1,
which is formed in the reaction of (2,4,6C,H,tBu,)COCI with Li[Sb(SiMe,),(dme)] . The Xray crystal structure analysis of 1 indicates a degree
of double-bond delocalization that, in addition to
steric bulk, stabilizes this unusual molecule.
P. B. Hitchcock, C. Jones,
J. F. Nixon* ...............................
m u g m u
\\ mu
Sb-Sb
\\
fBu C-OSiMe3
,&mu
490-492
Common Origin of Enthalpic and Entropic
Substituent Effects in Reactions of
Benzhydryl Cations with Nucleophiles
492-493
The First Distibabutadiene: Synthesis and
Structure of truns-l,4-Bis(trimethylsiloxy)-
1,4-bis(2,4,6-tri-tert-butylphenyl)-2,3-distibabutadiene
mu
1
* Author to whom correspondence should be addressed
BOOKS
K . Wundelt .........................................
495
H . Heitele ..........................................
495
Crystallography Made Crystal Clear. A Guide for Users of Macromolecular
Models * G. Rhodes
PV Suenger .........................................
496
Applications of Mass Spectrometry to Organic Stereochemistry * P. G. Mezey
H . Luftmann ......................................
497
Spectroscopy in Catalysis. An Introduction
J. W. Niemantsverdriet
Fundamentals of Photoinduced Electron Transfer
Sources 379
G. J. Kavarnos
Events 377
Preview 500
Author Index 499
376
0 VCH Verlagsgesellschafz mbH, 0-69451 Weinheim. 1995
Keyword Index 498
0570-0833/95/0404-0376$10.00+ ,2510
Angew. Chem. Int. Ed. Engl. 1995, 34, N o . 4
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