- Total synthesis of (-)-rhizopodin
-
Core assembly: The total synthesis of the myxobacterial metabolite rhizopodin, a potent actin-binding anticancer agent, has been achieved. The modular synthesis utilizes a common C1-C22 monomeric unit to assemble the dimeric 38-membered macrodiolide core, which was elaborated by a bidirectional boron-mediated aldol reaction to install the characteristic side-chains. The final global deprotection was critically dependent on the correct choice of silyl protecting groups at C16/C16′. Copyright
- Dalby, Stephen M.,Goodwin-Tindall, Jake,Paterson, Ian
-
-
Read Online
- Construction of Vicinal Quaternary Centers via Iridium-Catalyzed Asymmetric Allenylic Alkylation of Racemic Tertiary Alcohols
-
Enantioselective bond formation between sterically hindered fragments to furnish acyclic products with vicinal quaternary centers is a formidable challenge. We report a solution that involves cocatalysis between a chiral Ir-(phosphoramidite,olefin) complex and La(OTf)3. This robust catalytic system effects highly enantioconvergent and regioselective alkylation of racemic tertiary α-allenyl alcohols with tetrasubstituted silyl ketene acetals. The transformation displays broad functional group tolerance for both reaction components and allows efficient generation of β-allenyl ester products in good yield and with excellent enantioselectivity. Furthermore, both the allene and ester functionalities were leveraged to upgrade the structural complexity of the products via a series of stereoselective metal-catalyzed functionalization reactions.
- Isomura, Mayuko,Petrone, David A.,Carreira, Erick M.
-
supporting information
p. 3323 - 3329
(2021/04/07)
-
- C?Boron Enolates Enable Palladium Catalyzed Carboboration of Internal 1,3-Enynes
-
A new family of carbon-bound boron enolates, generated by a kinetically controlled halogen exchange between chlorocatecholborane and silylketene acetals, is described. These C?boron enolates are demonstrated to activate 1,3-enyne substrates in the presence of a Pd0/Senphos ligand complex, resulting in the first examples of a carboboration reaction of an alkyne with enolate-equivalent nucleophiles. Highly substituted dienyl boron building blocks are produced in excellent site-, regio-, and diastereoselectivity by the described catalytic cis-carboboration reaction.
- Wang, Ziyong,Wu, Jason,Lamine, Walid,Li, Bo,Sotiropoulos, Jean-Marc,Chrostowska, Anna,Miqueu, Karinne,Liu, Shih-Yuan
-
supporting information
p. 21231 - 21236
(2021/09/02)
-
- Eosin Y- and Copper-Catalyzed Dark Reaction to Construct Ene-γ-Lactams
-
Eosin Y, a common organo-photocatalyst in visible-light photoredox processes, was found to show excellent catalytic activities for thermal redox reactions under a catalytic amount of Cu(OAc)2. With this catalytic system, vinyl azides and ketene silyl acetals combine to form formal [3 + 2] cycloadducts by α-ester radical addition without light irradiation. This method provides a mild and straightforward paradigm to prepare important synthons of five-membered ene-γ-lactams and bridge ring lactams. It is the first example of an eosin Y-catalyzed redox reaction in the dark.
- Lei, Wen-Long,Feng, Kai-Wen,Wang, Tao,Wu, Li-Zhu,Liu, Qiang
-
supporting information
p. 7220 - 7224
(2018/11/25)
-
- Gallium trihalide catalyzed sequential addition of two different carbon nucleophiles to esters by using silyl cyanide and ketene silyl acetals
-
A sequential addition of silyl cyanide and ketene silyl acetals to esters was achieved by a gallium trihalide catalyst to produce β-cyano-β- siloxy esters. This is the first example of the sequential addition of two different carbon nucleophiles to esters. The employment of lactones provided α,α-disubstituted cyclic ethers with a cyano group and an ester moiety. A variety of esters and lactones are applicable to this reaction system.
- Inamoto, Yoshihiro,Kaga, Yuta,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
-
supporting information
p. 11664 - 11668
(2014/10/15)
-
- Synthetic studies on the pederin family of antitumour agents. Syntheses of mycalamide B, theopederin D and pederin
-
The synthesis of mycalamide B, theopederin D and pederin, which are antitumour agents was discussed. All three compounds were prepared from 6-lithio-2,3-dimethyl-4-phenylselenomethyl-3,4-dihydro-2H-pyran and 2-(3-chloropropyl)-3,3-dimethyl-3,4-dihydro-2H-pyran-4-one. Ground state conformational models were proposed to explain the stereoselectivity of the reactions. The absolute and relative stereochemistry of the compounds has been established by X-ray crystallography and NMR studies.
- Kocienski, Philip,Narquizian, Robert,Raubo, Piotr,Smith, Christopher,Farrugia, Louis J.,Muir, Kenneth,Boyle, F. Thomas
-
p. 2357 - 2384
(2007/10/03)
-
- A synthesis of mycalamide B
-
Mycalamide B, a potent antitumour agent, was synthesised from cheap, readily available starting materials: ethyl lactate, ethyl isobutyrate, 4-chlorobutanal, and 4-chlorobutanoyl chloride. The trioxabicyclo[4.4.0]decane ring system was created by reaction of a methoxymethyl ether with a silyloxyoxirane induced by phosphorus pentoxide.
- Kocienski, Philip J.,Narquizian, Robert,Raubo, Piotr,Smith, Christopher,Boyle, F. Thomas
-
p. 869 - 872
(2007/10/03)
-
- The Synthesis of O-Silyl Ketene Acetals from α-Haloesters
-
α-Haloesters of the general structure R1R2CXCO2R3 1 have been shown to react with sodium in the presence of a halosilane 2 to yield the corresponding O-silyl ketene acetals 3 (SKAs) according to equation 4.The factor that most influences the yields in these reactions is the concentration of halosilane; if there is a deficiency of halosilane, then acyloin condensation products will detract from the yield of SKAs.The reaction is quite general, and often gives yields in excess of 90percent of the desired SKAs.
- Schulz, William J.,Speier, John L.
-
p. 163 - 166
(2007/10/02)
-
- Synthesis and Conformation of 4,4,5,5-Tetramethyl-1,2-dithiane Mono-S-oxide
-
The synthesis of the title compound (6), an interesting subject for the study of anomeric and other conformational effects, was attained from ethyl isobutyrate in eight steps, with an overall yield of 11percent.The synthetic route described herein involved the crucial displacement of both neopentylic tosylate groups in 2,2,3,3-tetramethyl-1,4-butanediol ditosylate; while several standard procedures led to the formation of unexpected products, purified potassium thioacetate in hexamethylphosphoramide afforded the required dithioacetate derivative.The mechanistic implications of the well- and bad-behaved reactions are discussed.From the results of variable-temperature NMR experiments it is concluded that the axial conformer of 6 dominates the equilibrium to such an extent that no contribution of the equatorial isomer is recorded.This result sudggests a ΔG0 3.0 kcal/mol for the conformational equilibrium of the parent 1,2-dithiane mono-S-oxide.
- Juaristi, Eusebio,Cruz-Sanchez, J. Samuel
-
p. 3334 - 3338
(2007/10/02)
-
- NOUVELLES METHODES DE DESHALOGENATION ET DE FORMATION D'ALKYLTRIMETHYLACETALS DE CETENE PAR ACTION DE iPr2NLi SUR QUELQUES α-BROMOESTERS
-
A previously described method consisting in reacting LDA with α-bromoketones has been extended to α-bromoesters.Deshalogenation (after hydrolysis) and formation of ketene alkyltrimethylsilyl acetals (after SiMe3Cl addition) occur and show the generality of the method.
- Lion, Claude,Lebbar, Kadija,Boukou-Poba, Jean-Paul
-
p. 227 - 234
(2007/10/02)
-
- ON THE KETENE ALKYLSILYL ACETAL PREPARATIONS
-
The action of zinc powder with α-bromoesters in the presence of trimethylsilylchloride and TMEDA-Et3N led mainly to E-ketenealkylsilylacetals while the reaction of trialkylsilanes on alkyl acrylates catalyzed by Wilkinson reagent gave stereoselectively th
- Slougui, N.,Rousseau, G.
-
-
- ETUDE DE LA REACTION CHLOROCARBENE-ACETALS DE CETENES. I. SYNTHESE D'ESTERS α,β-ETHYLENIQUES.
-
The reaction of chloro, chloromethyl and chlorophenyl carbenoids with ketene alkylsilylacetals has been studied.Excellent yields of cyclopropanation were observed and the unstable chlorocyclopropanone acetals formed were thermally rearranged in high yield into α-substituted α,β-ethylenic esters.This new method for the synthesis of unsaturated esters appeared complementary of the known-ones.
- Slougui, N.,Rousseau, G.
-
p. 2643 - 2652
(2007/10/02)
-