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1.
KE Ylijoki PH Budzelaar JM Stryker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9894-9900
Alkyl-substituted η(5) -pentadienyl half-sandwich complexes of cobalt have been reported to undergo [5+2] cycloaddition reactions with alkynes to provide η(2) ,η(3) -cycloheptadienyl complexes under kinetic control. DFT studies have been used to elucidate the mechanism of the cyclization reaction as well as that of the subsequent isomerization to the final η(5) -cycloheptadienyl product. The initial cyclization is a stepwise process of olefin decoordination/alkyne capture, C?C bond formation, olefin arm capture, and a second C?C bond formation; the initial decoordination/capture step is rate-limiting. Once the η(2) ,η(3) -cycloheptadienyl complex has been formed, isomerization to η(5) -cycloheptadienyl again involves several steps: olefin decoordination, β-hydride elimination, reinsertion, and olefin coordination; also here the initial decoordination step is rate limiting. Substituents strongly affect the ease of reaction. Pentadienyl substituents in the 1- and 5-positions assist pentadienyl opening and hence accelerate the reaction, while substituents at the 3-position have a strongly retarding effect on the same step. Substituents at the alkyne (2-butyne vs. ethyne) result in much faster isomerization due to easier olefin decoordination. Paths involving triplet states do not appear to be competitive. 相似文献
2.
L. Weber S. Uthmann S. Kleinebekel H.‐G. Stammler A. Stammler B. Neumann 《无机化学与普通化学杂志》2000,626(8):1831-1836
Syntheses and Structures of η1‐Phosphaallyl, η1‐Arsaallyl, and η1‐Stibaallyl Iron Complexes [(η5‐C5Me5)(CO)2Fe–E(SiMe3)C(OSiMe3)=CPh2] (E = P, As, Sb) The reaction of equimolar amounts of [(η5‐C5Me5)(CO)2Fe–E(SiMe3)2] ( 1 a : E = P; 1 b : As; 1 c : Sb) and diphenylketene afforded the η1‐phosphaallyl‐, η1‐arsaallyl‐, and η1‐stibaallyl complexes [(η5‐C5Me5)(CO)2Fe–E(SiMe3)C(OSiMe3)=CPh2] ( 2 a : E = P; 2 b : As; 2 c : Sb). The molecular structures of 2 b and 2 c were elucidated by single crystal X‐ray analyses. 相似文献
3.
π‐Allyl (η3‐C3H5), a four‐electron donor, was used as a ligand model to replace η5‐C5Me4SiMe3 in DFT calculations on the tetranuclear yttrium polyhydrido complex (η5‐C5Me4SiMe3)4Y4H8 containing a Y4H8 tetrahedral core structure, which may separate the four π‐allyl groups and hence suppress the allyl ligand coupling during the computation. In terms of the calculated core geometry, isomerization energy barrier, charge population, and frontier orbital features of the complex, the η3‐C3H5 ligand model is comparable to η5‐C5H5. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
4.
Wu Fan Shengming Ma 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(52):14770-14773
A novel copper(I)‐catalyzed three‐component reaction for the efficient synthesis of 3‐amino‐2‐pyrones and 2,5‐dihydrofurans from propargyl alcohols, aldehydes, and amines has been developed. The starting materials are easily available and the scope of this method is broad. Through mechanistic studies, it is believed that the three‐component reaction consists of an A3‐coupling to propargylic amine, alkyne–allene isomerization, and intramolecular cyclization of the allenol to form a furan. In case of using ethyl glyoxalate as the aldehyde, a ring‐opening, lactonization, and isomerization process affords the 3‐amino‐2‐pyrones. 相似文献
5.
Copper(I)‐Catalyzed Three‐Component Reaction of Terminal Propargyl Alcohols,Aldehydes, and Amines: Synthesis of 3‐Amino‐2‐pyrones and 2,5‐Dihydrofurans
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Wu Fan Prof. Dr. Shengming Ma 《Angewandte Chemie (International ed. in English)》2014,53(52):14542-14545
A novel copper(I)‐catalyzed three‐component reaction for the efficient synthesis of 3‐amino‐2‐pyrones and 2,5‐dihydrofurans from propargyl alcohols, aldehydes, and amines has been developed. The starting materials are easily available and the scope of this method is broad. Through mechanistic studies, it is believed that the three‐component reaction consists of an A3‐coupling to propargylic amine, alkyne–allene isomerization, and intramolecular cyclization of the allenol to form a furan. In case of using ethyl glyoxalate as the aldehyde, a ring‐opening, lactonization, and isomerization process affords the 3‐amino‐2‐pyrones. 相似文献
6.
Barnali Dutta Basile F. E. Curchod Pablo Campomanes Dr. Euro Solari Dr. Rosario Scopelliti Dr. Ursula Rothlisberger Prof. Kay Severin Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(28):8400-8409
Cyclopentadienyl–ruthenium half‐sandwich complexes with η2‐bound alkyne ligands have been suggested as catalytic intermediates in the early stages of Ru‐catalyzed reactions with alkynes. We show that electronically unsaturated complexes of the formula [RuCl(Cp^)(η2‐RC≡CR′)] can be stabilized and crystallized by using the sterically demanding cyclopentadienyl ligand Cp^ (Cp^=η5‐1‐methoxy‐2,4‐tert‐butyl‐3‐neopentyl‐cyclopentadienyl). Furthermore we demonstrate that [RuCl2(Cp^)]2 is an active and regioselective catalyst for the [2+2+2] cyclotrimerization of alkynes. The first elementary steps of the reaction of mono(η2‐alkyne) complexes containing {RuCl(Cp*)} (Cp*=η5‐C5Me5) and {RuCl(Cp^)} fragments with alkynes were investigated by DFT calculations at the M06/6‐31G* level in combination with a continuum solvent model. Theoretical results are able to rationalize and complement the experimental findings. The presence of the sterically demanding Cp^ ligand increases the activation energy required for the formation of the corresponding di(η2‐alkyne) complexes, enhancing the initial regioselectivity, but avoiding the evolution of the system towards the expected cyclotrimerization product when bulky substituents are present. Theoretical results also show that the electronic structure and stability of a metallacyclic intermediate is strongly dependent on the nature of the substituents present in the alkyne. 相似文献
7.
Syntheses, Structure and Reactivity of η3‐1,2‐Diphosphaallyl Complexes and [{(η5‐C5H5)(CO)2W–Co(CO)3}{μ‐AsCH(SiMe3)2}(μ‐CO)] Reaction of ClP=C(SiMe2iPr)2 ( 3 ) with Na[Mo(CO)3(η5‐C5H5)] afforded the phosphavinylidene complex [(η5‐C5H5)(CO)2Mo=P=C(SiMe2iPr)2] ( 4 ) which in situ was converted into the η1‐1,2‐diphosphaallyl complex [η5‐(C5H5)(CO)2Mo{η3‐tBuPPC(SiMe2iPr)2] ( 6 ) by treatment with the phosphaalkene tBuP=C(NMe2)2. The chloroarsanyl complexes [(η5‐C5H5)(CO)3M–As(Cl)CH(SiMe3)2] [where M = Mo ( 9 ); M = W ( 10 )] resulted from the reaction of Na[M(CO)3(η5‐C5H5)] (M = Mo, W) with Cl2AsCH(SiMe3)2. The tungsten derivative 10 and Na[Co(CO)4] underwent reaction to give the dinuclear μ‐arsinidene complex [(η5‐C5H5)(CO)2W–Co(CO)3{μ‐AsCH(SiMe3)2}(μ‐CO)] ( 11 ). Treatment of [(η5‐C5H5)(CO)2Mo{η3‐tBuPPC(SiMe3)2}] ( 1 ) with an equimolar amount of ethereal HBF4 gave rise to a 85/15 mixture of the saline complexes [(η5‐C5H5)(CO)2Mo{η2‐tBu(H)P–P(F)CH(SiMe3)2}]BF4 ( 18 ) and [Cp(CO)2Mo{F2PCH(SiMe3)2}(tBuPH2)]BF4 ( 19 ) by HF‐addition to the PC bond of the η3‐diphosphaallyl ligand and subsequent protonation ( 18 ) and/or scission of the PP bond by the acid ( 19 ). Consistently 19 was the sole product when 1 was allowed to react with an excess of ethereal HBF4. The products 6 , 9 , 10 , 11 , 18 and 19 were characterized by means of spectroscopy (IR, 1H‐, 13C{1H}‐, 31P{1H}‐NMR, MS). Moreover, the molecular structures of 6 , 11 and 18 were determined by X‐ray diffraction analysis. 相似文献
8.
Dr. Thomas Weisheit Dr. Antje Kriltz Dr. Helmar Görls Prof. Dr. Grzegorz Mlostoń Prof. Dr. Wolfgang Imhof Prof. Dr. Wolfgang Weigand 《化学:亚洲杂志》2012,7(6):1383-1393
Two unsymmetrical 1,2,4‐trithiolanes ( 1d and 1e ) were reacted with [Pt0(PPh3)2(η2‐nbe)] ( 6 ; nbe=norborn‐2‐ene) and [Pt0(dppn)(η2‐nbe)] ( 11 ; dppn=1,8‐bis(diphenylphosphanyl)naphthalene)), respectively. Their treatment with compound 6 resulted in the formation of six‐membered platinacycles of type 7 , which selectively underwent fragmentation into dithiolato complexes and thiobenzophenone ( 4b ). The isolation of the first stable C‐substituted member of this class of compounds (i.e., compound 7e ) permitted kinetic studies of this process by using UV/Vis spectroscopy. These results, together with DFT calculations, allowed us to propose a mechanism for the reactions of compound 6 with 1,2,4‐trithiolanes. In contrast, similar treatment of compound 11 with compounds 1d and 1e at room temperature did not result in any reaction. Heating the appropriate samples to 110 °C led to the formation of dithiolato complexes and η2‐thioketone compounds, thus pointing to a thermally induced [3+2]‐cycloreversion of the heterocycles as an initial step of the reaction. 相似文献
9.
Guangyong Xie Changtao Qian 《Journal of polymer science. Part A, Polymer chemistry》2008,46(1):211-217
A series of new mono β‐diiminato titanium complexes [(N(Ar)C(CH3))2 CH]TiCl3 ( 3a : Ar = 2.6‐F2C6H3; 3b : Ar = C6F5; 3c : Ar = 2.6‐Me2C6H3) have been synthesized and characterized. The crystal structure of 3a revealed that the β‐diiminato ligand in our complex is more close to the η2‐coordination mode with little delocalization of the double bonds, which is different from the strong delocalization in the ligands of η5‐coordinated (Tolnacnac)TiCl3 and η2‐coordinated (Dipnacnac)ZrCl3. The significant electronic effects of fluoro‐substituents on the olefin polymerization activity of mono β‐diiminato titanium complexes were found. Titanium complexes with fluorine‐containing β‐diiminato ligands, on activation with MMAO, are extremely active catalysts for polymerization of ethylene. The activity of copolymerization of ethylene and 1‐hexene is higher than homopolymerization of ethylene and increases with the increase of 1‐hexene concentrations, which show the positive “comonomer effect.” The molar percentage of 1‐hexene incorporation and polymer microstructures can also be modulated by the initial comonomer concentrations. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 211–217, 2008 相似文献
10.
M. Sc. Shuai Shi M. Sc. Tao Wang Vanessa Weingand Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Angewandte Chemie (International ed. in English)》2014,53(4):1148-1151
The reaction of an α‐ketoaldehyde and a terminal alkyne in the presence of piperidine and a catalytic amount of AuCl delivers 1,2‐dicarbonyl‐3‐enes, products of the formal hydroacylation of the triple bond. The scope of the method is broad; different aryl substituents on the dicarbonyl unit and on the alkyne are well tolerated. The products can be transformed selectively into vinylquinoxalines. Mechanistic studies, including isotope‐labeling experiments, indicate that after an initial A3‐type conversion to propargylic amines, a subsequent base‐mediated alkyne‐to‐allene isomerization and a hydrolysis of the enamine substructure during the workup deliver the formal hydroacylation products. 相似文献
11.
Nilo Zanatta Elizandra C. S. Lopes Leonardo Fantinel Helio G. Bonacorso Marcos A. P. Martins 《Journal of heterocyclic chemistry》2002,39(5):943-947
The synthesis of a novel series of twelve 4‐(trihalomethyl)dipyrimidin‐2‐ylamines, from the cyclo‐condensation reaction of 4‐(trichloromethyl)‐2‐guanidinopyrimidine, with β‐alkoxyvinyl trihalomethyl ketones, of general formula: X3C‐C(O)‐C(R2)=C(R1)‐OR, where: X = F, Cl; R = Me, Et, ‐(CH2)2‐, ‐(CH2)3‐; R1 = H, Me; R2 = H, Me, ‐(CH2)2‐, ‐(CH2)3‐, is reported. The reactions were carried out in acetonitrile under reflux for 16 hours, leading to the dipyrimidin‐2‐ylamines in 65‐90% yield. Depending on the substituents of the vinyl ketone, tetrahydropyrimidines or aromatic pyrimidine rings were obtained from the cyclization reaction. When X = Cl, elimination of the trichloromethyl group was observed during the cyclization step. The structure of 4‐(trihalomethyl)dipyrimidin‐2‐ylamines was studied in detail by 1H‐, 13C‐ and 2D‐nmr spectroscopy. 相似文献
12.
Complexes of Titanium — Synthesis, Structure, and Fluxional Behaviour of CpTi{η6‐C5H4=C(p‐Tol)2}Cl (Cp′ = Cp*, Cp) The reaction of Cp′TiCl3 (C′ = Cp* or Cp) with magnesium and 6, 6‐di‐para‐tolylpentafulvene generates good yields of pentafulvene complexes Cp*Ti{η6‐C5H4=C(p‐Tol)2}Cl ( 4 ) and CpTi{η6‐C5H4=C(p‐Tol)2}Cl ( 5 ), respectively. The crystal and molecular structure of 4 have been determined from X‐ray data and exhibits compared to known η6‐pentafulvene complexes an unusual large Ti—C(p‐Tol)2 (Fv)‐distance (2.535(5)Å) evoked by the bulky substituents at the exocyclic carbon. Dynamic 1H‐NMR and spin saturation transfer experiments point out a rotation of the fulvene ligand around the Ti—Ct2 axis (Ct2 = centroid of the fulvene ring carbon atoms) with an activation barrier ΔG≠C = 60.6 ± 0.5 kJ mol−1 (TC = 314 ± 2 K). For 5 this barrier is significantly larger. Analogous dynamic behaviour is well known for diene complexes, but to our knowledge, it is here first‐time described for a pentafulvene complex. 相似文献
13.
Tarlok S. Lobana Prof. Parminderjit Kaur Geeta Hundal Ray J. Butcher Alfonso Castineiras 《无机化学与普通化学杂志》2008,634(4):747-753
Reactions of pyrimidine‐2‐thione (HpymS) with PdII/PtIV salts in the presence of triphenyl phosphine and bis(diphenylphosphino)alkanes, Ph2P‐(CH2)m‐PPh2 (m = 1, 2) have yielded two types of complexes, viz. a) [M(η2‐N, S‐ pymS)(η1‐S‐ pymS)(PPh3)] (M = Pd, 1 ; Pt, 2 ), and (b) [M(η1‐S‐pymS)2(L‐L)] {L‐L, M = dppm (m = 1) Pd, 3 ; Pt, 4 ; dppe (m = 2), Pd, 5 ; Pt, 6 }. Complexes have been characterized by elemental analysis (C, H, N), NMR spectroscopy (1H, 13C, 31P), and single crystal X‐ray crystallography ( 1 , 2 , 4 , and 5 ). Complexes 1 and 2 have terminal η1‐S and chelating η2‐N, S‐modes of pymS−, while other Pd/Pt complexes have only terminal η1‐S modes. The solution state 31P NMR spectral data reveal dynamic equilibrium for the complexes 3 , 5 and 6 , whereas the complexes 1 , 2 and 4 are static in solution state. 相似文献
14.
Dr. Randa K. Gabr Prof. Dr. Takuji Hatakeyama Prof. Dr. Kazuhiro Takenaka Prof. Dr. Shinobu Takizawa Yoshihiro Okada Prof. Dr. Masaharu Nakamura Prof. Dr. Hiroaki Sasai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(29):9518-9525
The reaction pathway of an enantioselective 5‐endo‐trig‐type cyclization of 3‐alkenoic acids catalyzed by a chiral palladium–spiro‐bis(isoxazoline) complex, Pd–SPRIX, has been studied by density functional theory calculations. The most plausible pathway involves intramolecular nucleophilic attack of the carboxylate moiety on the C?C double bond activated by Pd–SPRIX and β‐H elimination from the resulting organopalladium intermediate. The enantioselectivity was determined in the cyclization step through the formation of a π‐olefin complex, in which one of the two enantiofaces of the olefin moiety was selected. The β‐H elimination occurs via a seven‐membered cyclic structure in which the acetate ligand plays a key role in lowering the activation barrier of the transition state. In the elimination step, the SPRIX ligand was found to behave as a monodentate ligand due to the hemilability of one of the isoxazoline units thereby facilitating the elimination. Natural population analysis of this pathway showed that the more weakly electron‐donating SPRIX ligand, compared with the bis(oxazoline) ligand, BOX, facilitated the formation of the π‐olefin complex intermediate, leading to a smaller overall activation energy and a higher reactivity of the Pd–SPRIX catalyst. 相似文献
15.
Zhuliang Zhong Donghui Ma Gaoyuan Zhao Huilin Li Dengyu Xu Dr. Xingang Xie Prof. Dr. Xuegong She 《化学:亚洲杂志》2015,10(12):2599-2603
The first asymmetric total synthesis of kravanhin B has been accomplished with a linear reaction sequence of 13 steps starting from (R)‐(?)‐carvone. The synthesis features an intramolecular aldol cyclization to construct the desired cis‐fused decalin skeleton and an acid‐catalyzed dehydration and olefin isomerization to install the γ‐butenolide ring. 相似文献
16.
Yasuyuki Miyoshi Takeo Akatsuka Shin‐ichi Okuoka Aki Tsukajima Mitsuaki Makino Makoto Saito Dr. Koji Yonehara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(25):7941-7949
Further study of our aerobic intermolecular cyclization of acrylic acid with 1‐octene to afford α‐methylene‐γ‐butyrolactones, catalyzed by the Pd(OCOCF3)2/Cu(OAc)2 ? H2O system, has clarified that the accumulation of water generated from oxygen during the reaction causes deactivation of the Cu cocatalyst. This prevents regeneration of the active Pd catalyst and, thus, has a harmful influence on the progress of the cyclization. As a result, both the substrate conversion and product yield are efficiently improved by continuous removal of water from the reaction mixture. Detailed analysis of the kinetic and spectroscopic measurements performed under the condition of continuous water removal demonstrates that the cyclization proceeds in four steps: 1) equilibrium coordination of 1‐octene to the Pd acrylate species, 2) Markovnikov‐type acryloxy palladation of 1‐octene (1,2‐addition), 3) intramolecular carbopalladation, and 4) β‐hydride elimination. Byproduct 2‐acryloxy‐1‐octene is formed by β‐hydride elimination after step 2). These cyclization steps fit the Michaelis–Menten equation well and β‐hydride elimination is considered to be a rate‐limiting step in the formation of the products. Spectroscopic data agree sufficiently with the existence of the intermediates bearing acrylate (Pd? O bond), η3‐C8H15 (Pd? C bond), or C11H19O2 (Pd? C bond) moieties on the Pd center as the resting‐state compounds. Furthermore, not only CuII, but also CuI, species are observed during the reaction time of 2–8 h when the reaction proceeds efficiently. This result suggests that the CuII species is partially reduced to the CuI species when the active Pd catalytic species are regenerated. 相似文献
17.
Rhodium(II)‐Catalyzed Annulation of Azavinyl Carbenes Through Ring‐Expansion of 1,3,5‐Trioxane: Rapid Access to Nine‐Membered 1,3,5,7‐Trioxazonines
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Dr. Jola Pospech Dr. Raffaella Ferraccioli Dr. Helfried Neumann Prof. Dr. Matthias Beller 《化学:亚洲杂志》2015,10(12):2624-2630
The rhodium(II)‐catalyzed denitrogenative coupling of N‐alkylsulfonyl 1,2,3‐triazoles with 1,3,5‐trioxane led to nine‐membered‐ringed trioxazonines in moderate‐to‐good yields. 1,3,5‐Trioxane, acting as an oxygen nucleophile, reacted with the α‐aza‐vinylcarbene intermediate, giving rise to ylide formation, which was probably the key step in the reaction. Triazoles that contained aryl substituents with various electronic and steric features on the C4 carbon atom were well‐tolerated. The synthesis of trioxazonine derivatives was achieved through a one‐pot, two‐step procedure from 1‐mesylazide and a terminal alkyne by combining CuI‐catalyzed 1,3‐dipolar cycloaddition and rhodium‐catalyzed transformations. 相似文献
18.
Dr. Laura Rubio‐Pérez Dipl.‐Chem. Ramón Azpíroz Dr. Andrea Di Giuseppe Dr. Victor Polo Dr. Ricardo Castarlenas Prof. Jesús J. Pérez‐Torrente Prof. Luis A. Oro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15304-15314
A general regioselective rhodium‐catalyzed head‐to‐tail dimerization of terminal alkynes is presented. The presence of a pyridine ligand (py) in a Rh–N‐heterocyclic‐carbene (NHC) catalytic system not only dramatically switches the chemoselectivity from alkyne cyclotrimerization to dimerization but also enhances the catalytic activity. Several intermediates have been detected in the catalytic process, including the π‐alkyne‐coordinated RhI species [RhCl(NHC)(η2‐HC?CCH2Ph)(py)] ( 3 ) and [RhCl(NHC){η2‐C(tBu)?C(E)CH?CHtBu}(py)] ( 4 ) and the RhIII–hydride–alkynyl species [RhClH{? C?CSi(Me)3}(IPr)(py)2] ( 5 ). Computational DFT studies reveal an operational mechanism consisting of sequential alkyne C? H oxidative addition, alkyne insertion, and reductive elimination. A 2,1‐hydrometalation of the alkyne is the more favorable pathway in accordance with a head‐to‐tail selectivity. 相似文献
19.
A series of η5‐cyclopentadienylruthenium complexes, [(η5‐C5MenH5?n)RuCl(cod)] (cod=1,5‐cyclooctadiene), are evaluated as catalysts for the cycloaddition of 1,6‐diynes with alkynes. As a result, we unexpectedly found that the complex bearing the 1,2,4‐Me3Cp ligand is the most efficient catalyst in terms of turnover number (TON) for the cycloaddition of a bulky diiododiyne with acetylene, recording the highest TON of 970 with a catalyst loading of 0.1 mol %. To obtain insight into this result, we evaluate the electron richness of all complexes by cyclic voltammetric analyses, which indicate that the electron density of the ruthenium center increases with an increase in methyl substitution on the Cp′ ligands. The initial rate (up to 10 % conversion) of the cycloaddition was then measured using 1H NMR spectroscopy. The initial rate is found to decrease as the number of methyl substituents increases. According to these results, we assumed that the optimum catalytic performance exhibited by the 1,2,4‐trimethylcyclopentadienyl complex can be attributed to its robustness under the catalytic cycloaddition conditions. The steric and electronic effects of the Cp′ ligands are also investigated in terms of the regioselectivity of the cycloaddition of an unsymmetrical diyne and in terms of the chemoselectivity in the cycloaddition of a 1,6‐heptadiyne with norbornene. 相似文献
20.
Synthesis and Analysis of the Conformational Preferences of 5‐Aminomethyloxazolidine‐2,4‐dione Scaffolds: First Examples of β2‐ and β2, 2‐Homo‐Freidinger Lactam Analogues
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Arianna Greco Sara Tani Rossella De Marco Luca Gentilucci 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13390-13404
Constrained peptidomimetic scaffolds are of considerable interest for the design of therapeutically useful analogues of bioactive peptides. We present the single‐step cyclization of (S)‐ or (R)‐α‐hydroxy‐β2‐ or α‐substituted‐α‐hydroxy‐β2, 2‐amino acids already incorporated within oligopeptides to 5‐aminomethyl‐oxazolidine‐2,4‐dione (Amo) rings. These scaffolds can be regarded as unprecedented β2‐ or β2, 2‐homo‐Freidinger lactam analogues, and can be equipped with a proteinogenic side chain at each residue. In a biomimetic environment, Amo rings act as inducers of extended, semi‐bent or folded geometries, depending on the relative stereochemistry and the presence of α‐substituents. 相似文献