вход по аккаунту


Graphical Abstract (Angew. Chem. Int. Ed. Engl. 81994)

код для вставкиСкачать
A Journal of the
Deutscher Chemiker
International Edition in English
Pages 793 - 902
-dodecaynetruly an exploding [6]rotane- and the chair-shaped structure of its 30-membered
ring with six 1,3-butadiyne and six spirocyclopropane units. The compound is obtained in 39% yield from the oxidative coupling of two open-chain halves and
decomposes spontanteously upon heating or impact. The picture was put together
electronically from a videotape of the explosion and a representation of the crystal
structure (fototeam Hansjiirgen Gutzeit GmbH, Gottingen (FRG)). A. de Meijere
et al. report on this and related molecules on p. 869ff.
Con tents
Cyclodextrins are valuable components in supramolecular chemistry, as they are readily available, can be modified selectively, and serve as hosts for diverse guests by
means of noncovalent interactions. Fascinating molecular architectures such as
catenanes. rotaxanes, and tubes can be constructed. Interesting functions like catalysis, molecular recognition, and molecular transport can be performed. Applications in analysis, food chemistry, and pharmacology should provide motivation for
scientists to cross traditional interdisciplinary borders and search for new targets
constructed from cyclodextrins.
Methods from group theory and multivariate statistical techniques have turned the
structure correlation method developed 20 years ago into an even more powerful
instrument for structure-reactivity studies. Thus within the general scheme
sketched below for [ML,] complexes, short-lived tetrahedral Rh' and Ir' complexes
have been shown to be plausible intermediates along reaction path C, and doubt has
been cast on the common assumption that five-coordinate Pt" and Pd" compounds
undergo intramolecular ligand exchange by a Berry mechanism (path B).
Aiigoi . Clwiir. 1n1. Ed. Eiigl. 1994, 33.
i: C'CH Vr.rlu,
tnhH, 0-69451 Wcinlieim, 19Y4
G. Wenz* ...................................
803 -822
Cyclodextrins as Building Blocks for
Supramolecular Structures and Functional
T. Auf der Heyde* .....___........_....
Determination of Reaction Paths for Pentacoordinate Metal Complexes with the
Structure Correlation Method
057(i-08.?3:'94:/)80K-O7Yj R 10.00
+ .25:0
Immense ecological and technical importance is enjoyed by methanotrophic bacteria,
which can oxidize hydrocarbons to CO,. The key to understanding the mode of
action of the enzyme methane monooxygenase is held by the research groups of S. J.
Lippard and P. Nordlund, who unraveled the structure of the active site. The processes in the oxidation of methane by air to form methanol under physiological
conditions [Eq. (a)] will perhaps soon be elucidated on a molecular level.
+ NADH + H - + 0,
+ NAD' + H,O
B. Krebs,* N. Strater ................. 841 -843
X-Ray Structure Analysis of Methane Monooxygenase: An Important Step toward
Understanding the Oxidation of Methane
in Biological Systems
Fullerene-type structures in other areas of chemistry? Fullercages are elements in
feasible structure descriptions of a series of intermetallic phases. In contrast to the
carbon fullerenes, single bonds are proposed in these systems, and rather than
isolated cages, endohedral polyhedra and covalently bound adjacent cages are
found. As an example, Na,,In,,Z,.
Z = Ni, Pd, Pt, can be described as containing
Z(ii J n ((I Na 39 fo I n 7 5 .
R. Nesper * ................................
Fullercages without Carbon-Fulleranes,
Fullerenes, Space-filler-enes?
A Pt,, dendrimer is the highest nuclearity
complex obtained by the first convergent
method for the synthesis of alkyl transition
metal dendrimers. The product of the first
growth cycle is 1, which forms by oxidative
addition of 4,4'-bis(bromomethyl)-2,2'-bipyridine to [Me,Pt(tBu,bpy)] and subsequent
introduction of a Pt" center with [Pt,Me,(P-SMeJI '
S. Achar,
R. J. Puddephatt* ......................
Organoplatinum Dendrimers Formed by
Oxidative Addition
Me Me
Three hundred and twenty-seven atoms with a combined molecular weight of 9250.9 Da make up the
title compound, from which, as a cluster of the
mesoscopic range, one can expect unusual material
properties. A central O,, polyhedron (shown on the
right) defines the unusual cavity ofthis giant cluster
and points to interesting host -guest chemistry. The
cluster has been characterized by numerous analytical and spectroscopic methods.
A. Muller,* W Plass,
E. Krickemeyer, S. Dillinger,
H Bogge, A Armatage,
A. Proust, C Beugholt,
U. Bergmann
Four advantageous properties characterize mesitylborane MesBH, as a reagent: 1) It
is readily accessible and quite stable. 2) It can be treated with two different I-alkenes
in a stepwise fashion (-+ MesBR'R'). 3) The regioselectivity of each individual step
is > 9 9 % . 4) The products MesBR'R2 can be readily transformed via MeOBR'R'
or directly to BR' R2R3. MesBR'R' and BR1R2R3are important precursors for the
synthesis of ketones R'R'CO and tertiary alcohols R ' RZR3COH,respectively. by
the cyanoborate process.
K. Smith.* A. Pelter,*
Z. Jin .........................................
Only eight steps are required to synthesize the cytotoxic title compound 1 thanks to the unexpectedly
high eso selectivity in the key step. This selectivity
can most likely be attributed to steric factors; the
diene contains a geminal dimethyl group, the
dienophile a bulky aryl group.
849 - 851
- A
Highly Symmetrical Giant Cluster with an
Unusual Cavity and the Possibility of Positioning Paramagnetic Centers on Extremely
Large Cluster Surfaces
Synthesis and Properties of 2,4,6-Trimethylphenylborane (Mesitylborane), a
Stable Alternative to Thexylborane
T. Yoon, S. J. Danishefsky,*
S. de Gala ..................................
851 -853
A Concise Total Synthesis of (_+)-Mamanuthaquinone by Using an em-DielsAlder Reaction
Surprisingly, the "unnatural" aglycone analogue 1
(R = Ac) of calicheamicin cleaves double-stranded
DNA more effectively than the natural ent-1. If the
efficiency of this cleavage for the enediyne effector is
determined essentially by its configuration, the sequence selectivity of calicheamicin is rooted in the
saccharide recognition sector.
Ultimate convergence for the total
synthesis of calicheamicin 7: has
been achieved thanks to a remarkable glycosidation between the glycosy1 donor 2 and aglycone enf-1 (see
preceeding communication; R =
SSMe, ketal-protected); after glycosidation the natural product is obtained in two steps.
M ~ ~ C H N
J. Aiyar, S. A. Hitchcock.
D. Denhart, K. K. C. Liu,
S. J. Danishefsky,*
D. M. Crothers ..........................
On the DNA Recognition Role of the Carbohydrate Sector in Calicheamicin: A
Comparison of DNA Cleaving Capacity of
Enantiomeric Calicheamicinones
S. A. Hitchcock, S. H. Boyer,
M . Y. Chu-Moyer, S. H . Olson,
S. J. Danishefsky* ......................
A Convergent Total Synthesis of
Calicheamicin y',
Cryochemically prepared AlBr and AlBr, react in anisole to form donor-stabilized
A1Br2, which precipitates in the form of yellow needles with the composition
A12Br;2anisole. In the solid state the compound is stable at room temperature with
regard to disproportionation into A1 and All" species. The Al- Al distance in the
adduct (252.7 pm) is roughly as short as that in the radical anion [AI,R,]'(R = CH(SiMe,),), which contains an Al-Al o bond (253 pm) strengthened by E
bond contributions.
A new tricyclic framework is the characteristic feature of the violet, air-sensitive dyes 1. The phenyl
substituent X (X = Ph, 4-CF,-C,H4) is arranged orthogonally to the chromophore both in the crystal
and in solution, and the tricycle is bent by about 5"
about the axis C 9 - 0 10. In comparison to the frequently used rhodamines, compounds 1 absorb at
longer wavelengths and fluoresce with lower quantum yields.
M '
Donor-Stabilized Aluminum(I1) Bromide
L. Eggers, W. Grahn,*
W. Liittke, B. Knieriem,
P. G. Jones,
A. Chrapkowski ........................
863 -866
3,6-Diazaxanthylium Salts: Dyes with a
New Chromophore
The chirality of the propeller of the triphenylphosphane ligand is the only difference between the two
modifications of the organometallic complex salt 1.
Thus, in addition to the stereogenic ruthenium and
carbon centers, this complex has a further element
of chirality not represented in the formula depicted,
namely the propeller configuration of the PPh, ligand.
The oxidative coupling of the acyclic trimer of 1 ,I -diethynylcyclopropane gives title compound 1 as the
main product. X-ray structural analysis of 1 shows
that the spirocyclopropane and adjacent butadiyne
units have a distinct electronic interaction. A dehydrononamer (C63H36)was also isolated.
M. Mocker, C. Robl,
H. Schnockel* ...........................
H. Brunner,* R. Oeschey,
B. Nuber ....................................
Propeller Isomerism of the Triphenylphosphane Ligand in Half-Sandwich Ru" Complexes
A. de Meijere,*
S. Kozhushkov, C. Puls,
T. Haumann, R. Boese,
M. J. Cooney, L. T. Scott ........... 869-871
Hexaspiro[]dotetraconta-4,6,11,13,18,20,25,27,32,34,39.41dodecayne-An Exploding [6]Rotane
Angrw. Chrni. I n f Ed.
Engl. 1994. 33, No. 8
,Q VCH Ver/u~.sgese//schuft
nibH, D-6Y45f Wrinheim. 1994
0570-0X33i94,08OX-0797 B 10.00
+ .25:0
As if with a razor, single polypeptide chains
that extend significantly above the bulk layer
of polypeptides can be shaved off with alanine and leucine aminopeptidases. In the
preparation of tightly packed layers of helical
peptides, the lengths of the peptide chains
cannot be controlled; with the enzymatic
grooming process described here subsequent
smoothing is possible, which is important for
potential applications of these layers as
waveguide materials.
J. K. Whitesell,*
H. K. Chang,
C. S. Whitesell ...........................
Half a second in solution at room temperature is the
lifetime of didurylcarbene (1). This species is generated thermally and photochemically from the corresponding diazo compound and reacts by dimerization and by intramolecular H abstraction. The ortho
methyl groups are key to stabilizing the carbene, and
the meta methyl groups exert an additional buttressing effect.
H. Tomioka,* H. Okada,
T. Watanabe, K. Hirai ............... 873-875
871 -873
Enzymatic Grooming of Organic Thin
An Extremely Long-Lived Triplet Carbene;
Reactivity, Optical Absorption, and Kinetics of Highly Congested Diarylcarbenes
Optimally solvated Na' ions form in ethereal solutions when unsaturated hydrocarbons with extended rr-systems such as perylene undergo one-electron
reduction by sodium and crystallize as solvent-separated radical anion salts. The coordination number
of N a + is 6, 7, or 8 (see 1) depending on the ether
used as solvent. From the structural data approximate solvation enthalpies can be calculated, which
agree with laboratory experience.
H . Bock,* C. Niither,
Z. Havlas, A. John,
C. Arad ......................................
Ether-Solvated Sodium Ions in Salts Containing x-Hydrocarbon Anions: Crystallization, Structures, and Semiempirical Solvation Energies
Conglomerates of enantiomeric single crystals are formed on slow recrystallization of
the chiral nitroxide radicals 1. R = H, Me, obtained according to reaction (a). The
unusual arrangement of 1 in the crystal may explain the spontaneous optical resolution.
R. Tamura.* S. Susuki,
N. Azuma, A. Matsumoto,
F. Toda, A. Kamimura,
K . Hori ....................................
Preparation of Chiral Nitroxide Radicals
and Spontaneous Optical Resolution by
The first Nio complex with an arene as a sixelectron ligand, complex 1 is formed by the
displacement of the ethene ligands in [ ( q ' rBu,PCH,PtBu,)Ni(C,H,),1
by ethyne.
which undergoes cyclotrimerization on the
phosphane-nickel complex fragment at temperatures below -50 'C (!). The Ni atom in
1 has pseudo-linear coordination to the r y l bound diphosphane ligand and the planar,
symmetric benzene ligand.
T. Nickel, R. Goddard,
C. Kriiger,
K.-R. Porschke ..........................
Cyclotrimerization of Ethyne on the Complex Fragment [(q'-tBu,PCH,PrBu,)Ni']
with Formation of an q6-BenzeneNickel(o) Complex
Not the result of enzymatic degradation processes, but of the "preferential permeability" of the blood- brain barrier for (+ )-a-hexachlorocyclohexane (HCH)-this is
the interpretation of the selective accumulation of this enantiomer in seal brain. This
conclusion could be drawn only after the a-HCH isomers were successfullly separated on a chiral phase by HPLC. The structure of the (+) enantiomer was determined
by X-ray crystallography, but the structural elements responsible for the selective
transfer are still unknown.
K. Moller, C. Bretzke,
H. Hiihnerfuss,* R. Kallenborn,
J. N. Kinkel, J. Kopf,
G. Rimkus .................................
Doubly deprotonated monomeric units, chelation of
CU" ions, and stiffness iinparted by strong hydrogen bonds of the type 0 - H . . ' 0 - are characteristics of cellulose in Schweizer's reagent (shown on the
right). This solubilized form of cellulose discovered
in 1857 forms the basis of current technical processes for the preparation of membranes. The new findings were obtained from the combination of coordination chemistry and polymer analysis.
W. Burchard,*
N. Habermann, P. Kliifers.*
B. Seger, U. Wilhelm ................. 884-887
The Absolute Configuration of ( + ) - a 1,2,3,4,5,6-Hexachlorocyclohexane,
and Its
Permeation through the Seal Blood- Brain
Cellulose in Schweizer's Reagent: A Stable,
Polymeric Metal Complex with High Chain
The structure and the magnetic and electrochemical properties of the active center of
purple acid phosphatases are modeled by a complex that mimics the terminal coordination of the tyrosine residue and was prepared with a new heptadentate phenolato ligand system. The instability of the reduced Fe"Fe" state of the enzyme may be
attributed to the terminal ligand, since the phenolato ligand in the model is a
destabilizing factor.
E. Bernard, W. Moneta,
J. Laugier, S. Chardon-Noblat,
A. Deronzier, J.-P. Tuchagues,
J.-M. Latour* ............................
New, "three-dimensionally structured" porphyrins
were prepared in very few steps from /I,/Y-disubstituted pyrroles. In the corresponding biconcave
metalloporphyrins (shown on the right) the peripheral groups on both sides of the porphyrin plane
limit axial access to the metal center. For this reason
selective interactions with guest molecules and interesting catalyst properties can be expected.
Y Ramondenc,
R. Schwenninger, T. Phan,
K. Gruber, C. Kratky,
B. Krautler* ..............................
A new class of compounds, for example 2, synthesized from 1 or iodosobenzene, are
the title compounds in this article. The oxidation potential of 1 is increased considerably by bis(onio) substitution; thus, these new systems can be used as potent
oxidants. Applications include dehydrogenations of monohydrazones to give diazo
compounds and of 1,2-bishydrazones to give alkynes.
R. Weiss.* J. Seubert .................. 891 -893
A Mixed-Valent, Unsymmetrical Fe"Fe"'
Complex with a Terminal Phenolato Ligand as a Model for the Active Site of Purple
Acid Phosphatases
Porphyrins with Biconcave Frameworks
Electrostatic Activation of Hypervalent
Organo-Iodine Compounds : Bis(onio)Substituted Aryliodine(rr1) Salts
+ 2 Me,SiO,SCF,
- 2Me,SiOAc
The first crystalline iodocarbenium iodide 1
has an almost linear C-1-1 sequence, as
revealed by the X-ray structure analysis.
Thus 1 contains a new hypervalent threecenter. four-electron bonding system and
marks a characteristic point on the general reaction coordinate of the polar a-dihalogen elimination.
2 CF,SO;
R. Weiss,* M. Rechinger,
F. Hampel ..................................
Concerning the Mechanism of a-Elimination: Hypervalent Ion Pairing in an Iodocarbenium Iodide
Nitrito-U,O-copper complexes and dinitrogen oxide are the products of the reaction
of excess NO with the nitrosyl complexes [LCu(NO)] (L = substituted tris(pyrazoly1)hydroborate). a process that models environmentally important transforniations carried out by copper ions in proteins and zeolites. According to the results of
kinetic studies, the involvement of dimeric copper species in the rate-determining
step is ruled out, which suggests that NO coupling occurs at a single metal ion.
A tetragonal phase SrCuO, possibly causes the superconducting behavior of the
samples with the nominal composition Bi,Sr,CuO, prepared in the sol-gel process.
The results of the measurements indicate a critical temperature of 7 0 T , and the
superconductivity i s attributed to a phase present in the sample in less than 0.1 %.
Eight samples show evidence of room-temperature superconductivity, and an additional fourteen samples show superconductivity between 25 and 110 K.
C. E. Ruggiero, S. M. Carrier,
W. B. Tolman * ...........................
895 -897
Reductive Disproportionation of NO Mediated by Copper Complexes : Modeling
N,O Generation by Copper Proteins and
Heterogeneous Catalysts
R. S. Burrows,
D. H. McDaniel* ......................
Evidence of Room-Temperature Superconductivity in the Bi-Sr-Cu-0 System
* Author
to whom correspondence should be addressed
Histoire de la chimie B. Bensaude-Vincent, I. Stengers
The Fontana History of Chemistry * W. H. Brock
New Books
P. Laszlo ............................................
90 1
Author Index A-35
Preview A-36
The following reviews will appear in future issues:
Split Genes and RNA Splicing (Nobel Lecture)
P. A. Sharp
An Amazing Distortion in DNA Induced by a Methyltransferase (Nobel Lecture)
R. J. Robert
The Polymerase Chain Reaction (Nobel Lecture)
K. B. Mullis
Synthetic DNA and Biology (Nobel Lecture)
M. Smith
Fluorinated Isocyanides-More
D. Lentz
than Ligands with Unusual Properties
Peptidyl-Prolyl cisltrans Isomerases and Their Effectors
G. Fischer
Are Polar Organometallic Compounds “Carbanions”? The Gegenion Effect on Structure and Energies of Alkali Metal Compounds
C. Lambert, P. von R. Schleyer
Digitalis Research in Berlin-Buch-Retrospective and Perspective Views
K. R. H. Repke. R. Megges, J. Weiland, R. Schon
Gas-Phase Synthesis of Reactive Molecules Using Adsorbed Reagents
W. E. Billups, D. J. McCord
Без категории
Размер файла
466 Кб
abstract, int, angel, engl, chem, graphical, 81994
Пожаловаться на содержимое документа