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1.
4-(2'-Naphthoxy)-2-butenolide, readily available with high enantiopurity by a dynamic kinetic asymmetric transformation (DYKAT) of racemic 4-acyloxybutenolides (available in two steps from furfural), serves as an excellent chiral building block where the naphthoxy group strongly directs the stereochemistry of cycloadditions to the double bond. Notably, the cycloadditions of trimethylenemethanepalladium intermediates which do not exhibit good diastereoselectivity in additions to acceptors that possess many common and important chiral auxiliaries undergo cycloadditions with excellent regio- and stereocontrol. The utility of this process set the stage for an efficient new synthesis of (+)-brefeldin A, a compound of growing pharmacological significance. This synthesis also highlights the Pd-catalyzed DYKAT of crotyl carbonate to create the remote stereocenter. A new two-step method to convert aldehydes to delta-hydroxy-E-alpha,beta-enoates is also outlined. 相似文献
2.
[reaction: see text] A highly convergent total synthesis of (+)-brefeldin A that relies on a diastereoselective, beta-lactone-based cyclopentane synthesis combined with complex cross-metathesis reactions is described. The utility of beta-lactones for natural product synthesis and the versatility of cross-metathesis in this context were demonstrated, including the tolerance of an epimerizable aldehyde and a beta-lactone. 相似文献
3.
Lars Gnägi Severin Vital Martz Dr. Daniel Meyer Robin Marc Schärer Prof. Dr. Philippe Renaud 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(50):11646-11649
A very concise total synthesis of (+)-brefeldin C starting from 2-furanylcyclopentene is described. This approach is based on an unprecedented enantioselective radical hydroalkynylation process to introduce the two cyclopentane stereocenters in a single step. The use of a furan substituent allows a high trans diastereoselectivity to be achieved during the radical process and it contains the four carbon atoms C1–C4 of the natural product in an oxidation state closely related to the one of the target molecule. The eight-step synthesis requires six product purifications and it provides (+)-brefeldin C in 18 % overall yield. 相似文献
4.
An efficient formal synthesis of (+)-brefeldin A was accomplished through a synthetic approach that relied upon three keys steps. The five-membered ring was generated in a stereocontrolled fashion through application of a tandem conjugate addition-intramolecular cyclization method developed by Toru. Ring-closing metathesis provided access to a twelve-membered beta-keto lactone, which was ring-expanded to the alpha,beta-unsaturated-gamma-keto lactone through a zinc carbenoid-mediated reaction. Conversion of this lactone to (+)-brefeldin A has been reported previously. 相似文献
5.
A convergent selective route to (+)-brefeldin A (BFA) and 7-epi-BFA was developed, with the crucial C-4/C-5 stereogenic centers were established using Crimmins asymmetric aldolization. 相似文献
6.
We have gained some insight into the role of conformational effects on the regioselectivity of the macrocyclic intramolecular nitrile oxide cycloaddition observed in our (+)-brefeldin A synthesis. During the course of this regiochemical study, we have developed two novel stereoselective and regioselective schemes for total synthesis of (+)-brefeldin A (i.e. intramolecular nitrile oxide cycloaddition-isomerization and intermolecular nitrile oxide cycloaddition-ring closing metathesis strategies). 相似文献
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8.
Stefan Brse Dieter Enders Johannes Kbberling Frank Avemaria 《Angewandte Chemie (International ed. in English)》1998,37(24):3413-3415
Triazenes as “traceless” linkers for solid-phase synthesis have been utilized for the attachment of arenes to a solid support and yield the corresponding products after various organometallic reactions (Heck reaction and asymmetric dihydroxylation, see the reaction scheme) and cycloadditions (Diels–Alder reaction). The triazene linker is distinguished by its accessibility, thermal robustness, and capability to undergo regeneration. 相似文献
9.
N‐Heterocyclic Carbene Catalysis via Azolium Dienolates: An Efficient Strategy for Remote Enantioselective Functionalizations 下载免费PDF全文
Dr. Xiang‐Yu Chen Qiang Liu Dr. Pankaj Chauhan Prof. Dr. Dieter Enders 《Angewandte Chemie (International ed. in English)》2018,57(15):3862-3873
N‐heterocyclic carbene (NHC) catalysis has emerged as a powerful strategy in organic synthesis. In recent years a number of reviews have been published on NHC‐catalyzed transformations involving Breslow intermediates, acyl azoliums, α,β‐unsaturated acyl azoliums, homoenolate equivalents, and azolium enolates. However, the azolium dienolate intermediates generated by NHCs have been employed in asymmetric synthesis only very recently, especially in cycloadditions dealing with remote functionalization. This Minireview highlights all the developments and the new advances in NHC‐catalyzed asymmetric cycloaddition reactions involving azolium dienolate intermediates. 相似文献
10.
The efficient asymmetric synthesis of the antifungal pyrrolidine alkaloid (+)-preussin (2) was accomplished via the stereoselective reduction of a 5-substituted 3-oxo proline. The oxo proline was prepared from an N-sulfinyl δ-amino β-ketoester, a sulfinimine derived polyfunctionalized chiral building block. 相似文献
11.
Masayoshi Matsuzawa Hideaki Kakeya Junichiro Yamaguchi Mitsuru Shoji Rie Onose Hiroyuki Osada Yujiro Hayashi 《化学:亚洲杂志》2006,1(6):845-851
The asymmetric total synthesis of (+)‐panepophenanthrin, an inhibitor of ubiquitin‐activating enzyme (E1), has been accomplished using catalytic asymmetric α aminoxylation of 1,4‐cyclohexanedione monoethylene ketal as a key step, followed by several diastereoselective reactions. The biomimetic Diels–Alder reaction of a monomer precursor was found to proceed efficiently in water. The investigation of the biological properties of new derivatives of (+)‐panepophenanthrin enabled us to develop new cell‐permeable E1 inhibitors, RKTS‐80, ‐81, and ‐82. 相似文献
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13.
Trost BM Aponick A Stanzl BN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(34):9547-9560
The use of a mixture of dl- and meso-divinylethylene carbonate as an electrophile in palladium-catalyzed asymmetric allylic alkylation reactions is reported. From the diastereomeric mixture of meso and chiral racemic starting materials, a single product is obtained in high optical purity employing either oxygen or nitrogen nucleophiles. The resulting dienes have proven to be versatile synthetic intermediates as each carbon is functionalized for further transformation and differentiated by virtue of the reaction. A mechanism for this intriguing transformation is proposed and a concise enantioselective total synthesis of (+)-australine hydrochloride is reported as well as a formal synthesis of isoaltholactone. 相似文献
14.
An effective and enantioselective process for the total synthesis of (+)-brefeldin A (1) is described which starts from the dextrorotatory ketone2. 相似文献
15.
The practical and convergent total synthesis of (+)-brefeldin A has been achieved by an olefin disconnection strategy. Key features of the total synthesis include the efficient formation of C2 and C10 olefins, employing an olefin cross metathesis (CM) reaction and an intramolecular HWE olefination, respectively. 相似文献
16.
The asymmetric total synthesis of (-)-bipinnatin J and its conversion into (+)-intricarene through a transannular 1,3-dipolar cycloaddition is described. In addition, the conversion of (-)-bipinnatin J into (+)-rubifolide and (+)-isoepilophodione B is reported. Biosynthetic relationships among furanocembranoids and the possible role of 1,3-dipolar cycloadditions in biosynthesis are discussed. [reaction: see text] 相似文献
17.
Palladium-catalyzed asymmetric allylic alkylations (AAA) to form "chiral aldehyde" equivalents were investigated. Alpha-acetoxysulfones were formed in high enantiomeric excess as single regioisomers in AAA reactions of allylic geminal dicarboxylates with sodium benzenesulfinate. The directing ability of this novel functional group was highlighted by a series of dihydroxylations, affording syn diols exclusively anti to the acetoxy sulfone as single diastereomers in excellent yields. This is the first example of an asymmetric dihydroxylation protocol that gives the equivalent of reaction with a simple enal. The synthetic value of this process was exemplified by subsequent transformations of the diols including the development of a one-pot dihydroxylation-deprotective acyl migration protocol to give differentially protected 1,2-diols. 相似文献
18.
Suh YG Jung JK Seo SY Min KH Shin DY Lee YS Kim SH Park HJ 《The Journal of organic chemistry》2002,67(12):4127-4137
The total synthesis of (+)-brefeldin A has been accomplished via 15 linear steps in a 7.9% overall yield from the known Weinreb amide 6. The key parts of this approach include the stereoselective construction of the cis-disubstituted hydroxycyclopentane skeleton and the direct introduction of the C1-C3 acrylate moiety using a new variant of a trans-vinylogous acyl anion equivalent. 相似文献
19.
Laurent Comméiras John E. Moses Robert M. Adlington Andrew R. Cowley Birgit Albrecht 《Tetrahedron》2006,62(42):9892-9901
An asymmetric total synthesis of the novel and structurally complex epoxyquinol natural product (+)-panepophenanthrin has been accomplished, in which a biomimetic Diels-Alder dimerisation is a key step. The key monomeric precursor was assembled by an efficient Stille cross coupling of two readily available building blocks that upon standing underwent a diastereospecific dimerisation cascade in excellent yield. 相似文献
20.
Elias J. Corey Angel Guzman-Perez 《Angewandte Chemie (International ed. in English)》1998,37(4):388-401
A long-standing challenge to synthesis can now be met through the use of new and powerful catalytic asymmetric reactions for the assembly of complex chiral molecules with quaternary stereocenters from achiral building blocks. The reaction sequence shown below is just one example discussed in this review. 相似文献