- In situ generation of o-lodoxybenzoic acid (IBX) and the catalytic use of it in oxidation reactions in the presence of oxone as a co-oxidant
-
(Chemical Equation Presented) Catalytic use of o-iodoxybenzoic acid (IBX) in the presence of Oxone as a co-oxidant is demonstrated for the oxidation of primary and secondary alcohols in user- and eco-friendly solvent mixtures. Also demonstrated is the in situ (re)oxidation of 2-iodosobenzoic acid (IBA) and even commercially available 2-iodobenzoic acid (2IBAcid) by Oxone to IBX allowing one to use these less hazardous reagents, in place of potentially explosive IBX, as catalytic oxidants.
- Thottumkara, Arun P.,Bowsher, Michael S.,Vinod, Thottumkara K.
-
-
Read Online
- (P(C6H5)3)CpRu+-catalyzed deprotection of allyl carboxylic esters
-
A new and efficient catalytic method for deprotection of allyl carboxylic esters using a transition metal complex is reported. The reaction proceeds with a high substrate/catalyst ratio and without use of additional nucleophiles, giving the deprotected carboxylic acid in a quantitative yield. A variety of substrates, including the multifunctional amino acids and peptides, are also usable. The new method is more efficient, safe, and operationally simple in comparison to the conventional palladium-catalyzed method.
- Kitamura, Masato,Tanaka, Shinji,Yoshimura, Masahiro
-
-
Read Online
- Electrostatic complexation and photoinduced electron transfer between Zn-Cytochrome c and polyanionic fullerene dendrimers
-
Two dendritic fullerene (DF) monoadducts, 2 and 3, which can carry up to 9 and 18 negative charges, respectively, were examined with respect to electrostatic complexation with Cytochrome c (Cytc). To facilitate comprehensive photophysical investigations,
- Braun, Martin,Atalick, Stefan,Guldi, Dirk M.,Lanig, Harald,Brettreich, Michael,Burghardt, Stephan,Hatzimarinaki, Maria,Ravanelli, Elena,Prato, Maurizio,Van Eldik, Rudi,Hirsch, Andreas
-
-
Read Online
- An expedient strategy towards an advanced pyrrolidine intermediate for the synthesis of pyrrolizidine alkaloids
-
The asymmetric synthesis of a new pyrrolidine intermediate and a preceding amino triol derivative was accomplished using Crimmins' modified Evans aldol reaction as the key step. The synthetically useful pyrrolidine intermediate is expected to serve as the immediate precursor of biologically important pyrrolizidine alkaloids (-)-isoretronecanol and (-)-cremastrine. In addition, the amino triol subunit acts as a useful intermediate for the synthesis of oxocane heterocycles.
- Bera, Smritilekha,Mondal, Dhananjoy,Chatterjee, Bhaskar
-
-
Read Online
- A Novel Synthesis of Sex Pheromone from the Longicorn Beetle (Psacothea hilaris)
-
Abstract: An asymmetric synthesis of (8Z,21R)-21-methylpentatriacont-8-ene, the sex pheromoneof the yellow-spotted longicorn beetle Psacotheahilaris, has been achieved using Evan’s induction as the keystep. Based on the asymmetric methylation product of chiral (R)-4-benzyl-1,3-oxazolidin-2-one, the carbon chainof the target molecule was assembled through aC5+C12+C11+C8sequence. (2R)-4-(Benzyloxy)-2-methylbutan-1-ol, which can be obtained fromγ-lactone following Evan’s protocol, was connected to aC12 alkyl group. The chiral methyl group remained thekey moiety (97% ee). After another Wittigreaction and catalytic hydrogenation step, the designed key intermediate(13R)-13-methylheptacosan-1-ol wasobtained. Finally, after oxidation and Wittig reaction, the synthesis of thetarget molecule was completed in 10 linear steps with an ultra-high overallyield of 36.2%.
- He, Guo-Guo,Rao, Bao-Qi,Zhang, Tao,Zhang, Hong-Li,Bai, Hongjin,Du, Zhen-Ting
-
p. 455 - 461
(2021/04/13)
-
- Suppressing carboxylate nucleophilicity with inorganic salts enables selective electrocarboxylation without sacrificial anodes
-
Although electrocarboxylation reactions use CO2as a renewable synthon and can incorporate renewable electricity as a driving force, the overall sustainability and practicality of this process is limited by the use of sacrificial anodes such as magnesium and aluminum. Replacing these anodes for the carboxylation of organic halides is not trivial because the cations produced from their oxidation inhibit a variety of undesired nucleophilic reactions that form esters, carbonates, and alcohols. Herein, a strategy to maintain selectivity without a sacrificial anode is developed by adding a salt with an inorganic cation that blocks nucleophilic reactions. Using anhydrous MgBr2as a low-cost, soluble source of Mg2+cations, carboxylation of a variety of aliphatic, benzylic, and aromatic halides was achieved with moderate to good (34-78%) yields without a sacrificial anode. Moreover, the yields from the sacrificial-anode-free process were often comparable or better than those from a traditional sacrificial-anode process. Examining a wide variety of substrates shows a correlation between known nucleophilic susceptibilities of carbon-halide bonds and selectivity loss in the absence of a Mg2+source. The carboxylate anion product was also discovered to mitigate cathodic passivation by insoluble carbonates produced as byproducts from concomitant CO2reduction to CO, although this protection can eventually become insufficient when sacrificial anodes are used. These results are a key step toward sustainable and practical carboxylation by providing an electrolyte design guideline to obviate the need for sacrificial anodes.
- Corbin, Nathan,Lazouski, Nikifar,Manthiram, Karthish,Steinberg, Katherine,Yang, Deng-Tao
-
p. 12365 - 12376
(2021/10/08)
-
- Synthesis method of sex pheromone (S)-14-methyl-1-octadecene of lepidoptera pest peach leaf miners
-
The invention discloses a synthesis method of a sex pheromone (S)-14-methyl-1-octadecene of peach leaf miners, which comprises the following steps: carrying out ring opening on gamma-butyrolactone asa raw material, reacting the gamma-butyrolactone with benzyl chloride to generate 4-benzyloxybutyric acid, and reacting the 4-benzyloxybutyric acid with (S)-4-benzyl-2-oxazolidinone; performing reaction with methyl iodide under the action of organic base to induce chiral methyl; reducing the chiral methyl into alcohol under the action of lithium aluminum hydride, oxidizing the alcohol into aldehyde, and carrying out wittig reaction with triphenylpropylphosphonium bromide; after the Wittig reaction, using a Pt/C as a catalyst for catalytic hydrogenation to remove double bonds, removing benzyl with Pd/C as a catalyst to form alcohol, and oxidizing the alcohol into aldehyde; carrying out monobromination on 1, 10-decanediol, carrying out single protection by using TBSCl, and performing reaction with triphenylphosphine to obtain quaternary phosphonium salt; carrying out Wittig reaction on the aldehyde and the quaternary phosphonium salt, and using Pt/C as a catalyst for catalytic hydrogenation to eliminate double bonds; removing TBS single protection to form alcohol, and then oxidizing the alcohol into aldehyde; and reacting the aldehyde with methyltriphenylphosphonium bromide wittig toobtain the pheromone (S)-14-methyl-1-octadecene. According to the method, the reaction conditions are mild, chiral methyl is kept in the reaction process, and racemization is avoided.
- -
-
Paragraph 0047; 0049-0050
(2020/08/02)
-
- Asymmetric total synthesis method of sex pheromone (R, Z)-21-methyl-8-tripentadecene of psacothea hilaris
-
The invention discloses an asymmetric total synthesis method of sex pheromone (R, Z) 21-methyl-8-tripentadecene of psacothea hilaris, the method comprises the following steps: by using a compound 14 as an initial raw material, assembling a molecular carbon chain according to the sequence of C5+C12+C11+C8; firstly carrying out Wittig reaction with C12 quaternary phosphonium salt, and then carryingout another Wittig reaction and catalytic hydrogenation to obtain the key intermediate (R)-13-methylheptanoic acid-1-alcohol. Finally, after primary oxidation and Wittig reaction, obtaining the sex pheromone of the psacothea hilaris, wherein the total yield is 36.2%. According to the invention, the problems of lengthy synthesis steps, difficult resolution and low yield of non-chiral raw materialsin chiral pheromone synthesis are solved, and the asymmetric total synthesis of the sex pheromone (R,Z)21-methyl-8-tripentadecene of psacothea hilaris is completed. The method has the advantages of high yield, simple and convenient chemical operation and competitiveness in the aspect of cost control.
- -
-
Paragraph 0048; 0059
(2020/12/30)
-
- Oxidation of Alkynyl Boronates to Carboxylic Acids, Esters, and Amides
-
A general efficient protocol was developed for the synthesis of carboxylic acids, esters, and amides through oxidation of alkynyl boronates, generated directly from terminal alkynes. This protocol represents the first example of C(sp)?B bond oxidation. This approach displays a broad substrate scope, including aryl and alkyl alkynes, and exhibits excellent functional group tolerance. Water, primary and secondary alcohols, and amines are suitable nucleophiles for this transformation. Notably, amino acids and peptides can be used as nucleophiles, providing an efficient method for the synthesis and modification of peptides. The practicability of this methodology was further highlighted by the preparation of pharmaceutical molecules.
- Li, Chenchen,Li, Ruoling,Zhang, Bing,Zhao, Pei,Zhao, Wanxiang
-
supporting information
p. 10913 - 10917
(2020/05/25)
-
- Stereoselective synthesis of the Paulownia bagworm sex pheromone
-
According to our retrosynthesis, the main chain of the target molecule could be constructed using a C5?+?C7?+?C5 strategy. The key induction reaction afforded chiral methyl group moieties using different Evans templates with different configurations. Li2CuCl4 was effectively employed in the Csp3[sbnd]Csp3 coupling protocol. The target molecular was obtained in a 12.6% overall yield with nine steps in the longest linear route.
- Sun, Zhi-Feng,Zhou, Lu-Nan,Zhang, Tao,Du, Zhen-Ting
-
p. 558 - 562
(2017/06/19)
-
- Safe Removal of the Allyl Protecting Groups of Allyl Esters using a Recyclable, Low-Leaching and Ligand-Free Palladium Nanoparticle Catalyst
-
A safe, facile and low-leaching (up to 0.04ppm) method has been developed for the removal of allyl, prenyl and benzyl protecting groups from the corresponding esters, using a sulfur-modified gold-supported palladium (SAPd) nanoparticle catalyst, which is known to be non-flammable. The catalyst itself was found to be recyclable and the reaction appeared to proceed on the surface of the SAPd.
- Takagi, Koji,Fukuda, Hayato,Shuto, Satoshi,Otaka, Akira,Arisawa, Mitsuhiro
-
supporting information
p. 2119 - 2124
(2015/06/23)
-
- Unexpected dehomologation of primary alcohols to one-carbon shorter carboxylic acids using o-iodoxybenzoic acid (IBX)
-
A novel and efficient transformation of primary alcohols to one-carbon shorter carboxylic acids using IBX is reported. Mechanistic studies revealed that the combination of IBX and molecular iodine produces a different active hypervalent iodine species.
- Xu, Shu,Itto, Kaori,Satoh, Masahide,Arimoto, Hirokazu
-
supporting information
p. 2758 - 2761
(2014/03/21)
-
- Total synthesis of attenols A and B
-
A concise approach for the total synthesis of attenols A and B is described involving MacMillan's α-aminooxylation, Evan's asymmetric alkylation, Brown's allylation, and spiro-ketalization as key steps. This approach has successfully demonstrated the α-aminooxylation protocol for the construction of the anti-1,3-diol unit.
- Reddy, B.V. Subba,Reddy, B. Phaneendra,Swapnil,Yadav
-
p. 5781 - 5784
(2013/10/01)
-
- Synthesis of polyisoprene terpenoid dendrons and their applications in oligo(phenylene ethynylene)s as "shells"
-
The novel double-stage convergent synthesis of a new class of polyisoprene terpenoid (PIPTP) dendrons is described. PIPTP dendrons bear a highly branched aliphatic hydrocarbon skeleton and a hydrophilic hydroxy focal point functionality. These dendrons have the specific formula C (5×2G+1-5)H(5×2 G+2-8)O, and each dendritic layer is constructed from an isoprene unit. The key branching steps involve a double alkyl-metal addition to an ester functionality, followed by deoxygenation of the resulting tertiary alcohol by triethylsilane and trifluoroacetic acid, then hydrogenation or hydrogenolysis. The dendrons were also attached to oligo(phenylene ethynylene)s (OPEs) so as to function as protective shells to allow fine tuning of the nanoscopic environment around the OPE moiety, and to exert precise control of the packing density and intermolecular interaction between the OPE cores. Fluorescence quantum yield data reveal that the OPE core is better encapsulated by the PIPTP dendrons than by Frechet dendrons.
- Chai, Wen-Yu,Shi, Zi-Fa,An, Peng,Wang, Wei,Wang, Lu-Feng,Cao, Xiao-Ping
-
supporting information; experimental part
p. 143 - 155
(2012/03/26)
-
- Bivalent inhibitors for disrupting protein surface-substrate interactions and for dual inhibition of protein prenyltransferases
-
Low-molecular-weight compounds that disrupt protein-protein interactions (PPIs) have tremendous potential applications as clinical agents and as chemical probes for investigating intracellular PPI networks. However, disrupting PPIs is extremely difficult due to the large, flat interfaces of many proteins, which often lack structurally defined cavities to which drug-like molecules could bind in a thermodynamically favorable manner. Here, we describe a series of bivalent compounds that anchor to the enzyme active site to deliver a minimally sized surface-binding module to the targeted surface involved in transient PPI with a substrate. These compounds are capable of significantly inhibiting enzymatic reactions involving protein surface-substrate interaction in the single-digit nanomole range. Inhibitors of farnesyltransferase (FTase), which possesses a negatively charged local area on its α-subunit, were designed by attaching a module derived from a branched monoamine-containing gallate to a conventional active-site-directed CVTM tetrapeptide using an alkyl spacer. A significant improvement in inhibitory activity (>200-fold) against farnesylation of the K-Ras4B peptide was observed when the gallate module was attached to the CVTM tetrapeptide. Furthermore, the bivalent compounds had submicromolar inhibitory activity against geranylgeranylation of the K-Ras4B peptide catalyzed by GGTase I, which has an a-subunit identical to that of FTase. The anchoring strategy we describe would be useful for designing a new class of PPI inhibitors as well as dual enzyme inhibitors targeting common surface structures.
- Machida, Shinnosuke,Kato, Nobuo,Harada, Kazuo,Ohkanda, Junko
-
supporting information; experimental part
p. 958 - 963
(2011/04/16)
-
- Novel synthesis of amphiphilic dendrons by the double-stage convergent method
-
A serles of amphophilic dendrons (G1-G4) have been designed and synthesized, which have a highly branched aliphatic hydrocarbon skeleton and a hydrophilic hydroxyl functionality to enable conjugation with other substrates. The higher generation dendrons (G3 and G4) were synthesized by a double-stage convergent method, which shortened the synthetic route significantly and provided the products In an efficient manner. The key branching step involved a double alkyl-metal addition to an ester functionality followed by deoxygenation of a resulting tertiary alcohol by triethylsilane.
- Shi, Zi-Fa,Chai, Wen-Yu,An, Peng,Cao, Xiao-Ping
-
supporting information; experimental part
p. 4394 - 4397
(2009/12/26)
-
- Method of synthesis of water soluble fullerene polyacids using a malonate reactant
-
In one embodiment, the present invention is directed to a method for synthesizing compounds of the formula where Cm is a fullerene having m carbon atoms, the method comprising the steps of forming a linear malonate compound of the formula where each Z is the same or different and is a straight-chain or branched-chain aliphatic radical having from 1-30 carbon atoms which may be unsubstituted or monosubstituted or polysubstituted by identical or different substitutents, in which radicals up to every third —CH2— unit can be replaced by O or NR″, n is an integer from 2 to 10, and the unfilled valences of the first and nth malonate groups are filled with bonds to hydrogen, a hydrocarbon group or substituted hydrocarbon group having 1-20 carbon atoms, or a chain containing unsubstituted or substituted aryl or other cyclic groups; or (ii) a branched malonate compound of the formula where Z′ is an aliphatic radical having from 1-30 carbon atoms which may be unsubstituted or monosubstituted or polysubstituted by identical or different substitutents, in which radicals up to every third —CH2— unit can be replaced by O or NR″; and n is an integer from 2 to 10; reacting said malonate compound with Cm to form an adduct of the formula each Z is bonded to both one carboxylate group of a first malonate moiety and one carboxylate group of a second malonate moiety and the unfilled valences of the first and nth malonate groups are filled with bonds to hydrogen, a hydrocarbon group or substituted hydrocarbon group having 1-20 carbon atoms, or a chain containing unsubstituted or substituted aryl or other cyclic groups; and hydrolyzing said adduct to form the compound.
- -
-
Page/Page column 5-6; Sheet 12
(2008/06/13)
-
- Rapid assembly of matrix metalloprotease inhibitors using click chemistry
-
A panel of 96 metalloprotease inhibitors was assembled using "click chemistry" by reacting eight zinc-binding hydroxamate warheads with 12 azide building blocks. Screens of the bidentate compounds against representative metalloproteases provided discerning inhibition fingerprints, revealing compounds with low micromolar potency against MMP-7. The relative ease and convenience of the strategy in constructing focused chemical libraries for rapid in situ screening of MMPs is thereby demonstrated.
- Wang, Jun,Uttamchandani, Mahesh,Li, Junqi,Hu, Mingyu,Yao, Shao Q.
-
p. 3821 - 3824
(2007/10/03)
-
- "Click" synthesis of small molecule probes for activity-based fingerprinting of matrix metalloproteases
-
By using "Click Chemistry", we achieved the facile synthesis of various affinity-based hydroxamate probes that enable generation of activity-based fingerprints of a variety of metalloproteases, including matrix metalloproteases (MMPs), in proteomics experiments. The Royal Society of Chemistry 2006.
- Wang, Jun,Uttamchandani, Mahesh,Li, Junqi,Hu, Mingyu,Yao, Shao Q.
-
p. 3783 - 3785
(2007/10/03)
-
- TETRAHYDROFURAN PHOSPHATE- AND HYDROXY ESTERS, AS PRODRUGS FOR THE CORRESPONDING ANTIFUNGAL AGENT
-
A compound of formula (I) wherein G is H or PO3H2 or a pharmaceutical acceptable salt thereof, pharmaceutical compositions containing such compounds and method of using such compounds or pharmaceutical compositions containing them to treat or prevent fungal infection are disclosed.
- -
-
Page column 10-11
(2010/02/10)
-
- Regioselective synthesis and zone selective deprotection of [60]fullerene tris-adducts with an e,e,e addition pattern
-
D3h-symmetrical tripodal tris(malonate) tethers have been used for the synthesis of [60]fullerene tris-adducts with an e,e,e addition pattern bearing topologically distinct polar and equatorial addend zones that can selectively be deprotected. The Royal Society of Chemistry 2005.
- Beuerle, Florian,Chronakis, Nikos,Hirsch, Andreas
-
p. 3676 - 3678
(2007/10/03)
-
- Enantioselective total synthesis of the antitumor macrolide rhizoxin D
-
The convergent, highly enantioselective synthesis of rhizoxin D, a natural product possessing potent antitumor and antifungal bioactivity, is described. The C(1)-C(9) fragment of the molecule was synthesized utilizing a threefold pseudosymmetric intermediate ultimately derived from γ-butyrolactone. The central core of rhizoxin D was prepared via a chiral resolution/asymmetric aldol protocol. Several methods for the generation of the polyene fragment were explored, and the side-chain was ultimately prepared from serine in six steps. The unification of the left and right wings of the molecule was achieved using a one-step olefination protocol, and the macrocyclization was carried out using a Horner-Emmons olefination at the C(2)-C(3) olefin.
- Lafontaine, Jennifer A.,Provencal, David P.,Gardelli, Cristina,Leahy, James W.
-
p. 4215 - 4234
(2007/10/03)
-
- Substituted pyrazole compounds
-
Substituted pyrazole compounds represented by formula (I), or salts thereof are disclosed, wherein R1is —CH(OH)—CH(R4)—(A)n—Y, —CH2—CH(R4)—(A)n—Y, —CO—B1—A—Y or the like (wherein A is a lower alkylene; Y is an aryl group which may be substituted, for example, by halogen, or the like; R4is a hydrogen atom or a lower alkyl group; B1is —CH(R4)— or —N(R4)—; and n is 0 or 1); R2is a hydrogen atom, a lower alkyl group which may be substituted by hydroxyl or the like, or an aralkyl group; R3is a phenyl group which may be substituted by halogen or the like, or a pyridyl group; and Q is a pyridyl or quinolyl group. These substituted pyrazole compounds or their salts have an excellent p38MAP kinase inhibiting effect and are hence useful in the prevention or treatment of tumor necrosis factor α-related diseases, interleukin 1-related diseases, interleukin 6-related diseases or cyclooxygenase II-related diseases.
- -
-
Page column 28-29
(2010/02/06)
-
- SUBSTITUTED PYRAZOLE COMPOUNDS
-
Substituted pyrazole compounds represented by formula (I), or salts thereof are disclosed, wherein R1 is -CH(OH)-CH(R4)-(A)n -Y, -CH2 -CH(R4)-(A)n-Y, -CO-B1-A-Y or the like (wherein A is a lower alkylene; Y is an aryl group which may be substituted, for example, by halogen, or the like; R4 is a hydrogen atom or a lower alkyl group; B1 is -CH(R4)- or -N(R4)-; and n is 0 or 1); R2 is a hydrogen atom, a lower alkyl group which may be substituted by hydroxyl or the like, or an aralkyl group; R3 is a phenyl group which may be substituted by halogen or the like, or a pyridyl group; and Q is a pyridyl or quinolyl group. These substituted pyrazole compounds or their salts have an excellent p38MAP kinase inhibiting effect and are hence useful in the prevention or treatment of tumor necrosis factor α-related diseases, interleukin 1-related diseases, interleukin 6-related diseases or cyclooxygenase II-related diseases.
- -
-
-
- SOB as an alternate to BOB: Findings from the preparation of injectable antifungal Sch 59884
-
A facile preparation of 4-silyloxybutyrates (SOB) and their potential use as an alternate to 4-benzyloxybutyrate (BOB) are described.
- Renton,Gala,Lee
-
p. 7141 - 7143
(2007/10/03)
-
- Observation of the pathway from lysine to the isoprenoidal lipid of halophilic archaea, Halobacterium halobium and Natrinema pallidum, using regiospecifically deuterated lysine
-
We examined the incorporation of lysine into archaeal isoprenoidal lipids of halophilic archaea, Natrinema pallidum and Halobacterium halobium using two regiospecifically deuterium-labeled derivatives, [3,3-2H2] and [6,6-2H2]lysines. The two deuterated lysines were synthesized, and the incorporation of deuterium to the lipid core was defined by 2H NMR. The results revealed that lysine is degraded to crotonoyl-CoA by the decarboxylation of carboxylate in the metabolism of halophilic archaea, much like the metabolism of lysine in aerobic bacteria; the process converts lysine to isoprenoidal lipids via the mevalonate pathway through glutaryl-CoA, crotonoyl-CoA, and acetoacetyl-CoA.
- Yamauchi, Noriaki,Endoh, Satoshi,Kato, Keiko,Murae, Tatsushi
-
p. 2199 - 2205
(2007/10/03)
-
- Amidite derivatives and oligonucleotide derivatives
-
PCT No. PCT/JP96/00868 Sec. 371 Date Dec. 22, 1997 Sec. 102(e) Date Dec. 22, 1997 PCT Filed Mar. 29, 1996 PCT Pub. No. WO96/30386 PCT Pub. Date Oct. 3, 1996The present invention provides a compound of general formula (I): wherein X represents group (II) o
- -
-
-
- Tetrahydrofuran antifungal phosphate
-
A compound of the formula I STR1 wherein G is H or PO3 H2 or a pharmaceutical acceptable salt thereof, pharmaceutical compositions containing such compounds and method of using such compounds or pharmaceutical compositions containing them to treat or prevent fungal infection are disclosed.
- -
-
-
- Facile and clean oxidation of alcohols in water using hypervalent iodine(III) reagents
-
An environmentally benign oxidation of alcohols in water using iodosobenzene (PhI=O) or a polymer-supported (diacetoxyiodo)benzene (PSDIB) with KBr has been achieved (see scheme). This method results in the catalytic activation of a variety of sluggishly reactive and/or sparsely soluble hypervalent iodine reagents in water under neutral conditions.
- Tohma, Hirofumi,Takizawa, Shinobu,Maegawa, Tomohiro,Kita, Yasuyuki
-
p. 1306 - 1308
(2007/10/03)
-
- Synthetic studies toward potent cytotoxic agents amphidinolides G and H: Synthesis of the entire C15-C26 moiety of the top half
-
Stereoselective synthesis of the entire (16S, 18S, 21R, 22S, 23R, 25R)- C15-C26 segment 1 of amphidinolides G and H has been achieved for the first time following a highly efficient convergent strategy.
- Chakraborty,Suresh
-
p. 7775 - 7778
(2007/10/03)
-
- A novel method for suppression of the abnormal Fischer indole synthesis
-
A method is described for the use of the Fischer indole synthesis to prepare 7-hydroxy-indoles in good yield. The method involves the construction of a 4-aminobenzoxazine and removal of the N-O tether after the indole has been formed.
- Szczepankiewicz, Bruce G.,Heathcock, Clayton H.
-
p. 8853 - 8870
(2007/10/03)
-
- Rhizoxin synthetic studies. 1. Synthesis of the right hand [C(1) to C(9)]portion via a "pinwheel" approach
-
A concise synthetic approach to the C(1) - C(9) fragment of the antitumor macrolide rhizoxin via a three-fold pseudosymmetric intermediate is described. The preparation (from readily available γ-butyrolactone) includes both an asymmetric allylation and an
- Lafontaine, Jennifer A.,Leahy, James W.
-
p. 6029 - 6032
(2007/10/02)
-
- Chemoselective deprotection of benzyl esters in the presence of benzyl ethers, benzyloxymethyl ethers and N-benzyl groups by catalytic transfer hydrogenation
-
-COOBn, -PO(OH)OBn, -O-CBz and N-CBz groups are efficiently and chemoselectively deprotected in the presence of Bn and BOM ethers and N-Bn groups by hydrogenolysis under catalytic transfer hydrogenation using 10% palladium on carbon as the catalyst and cyclohexadiene as the hydrogen donor.
- Bajwa
-
p. 2299 - 2302
(2007/10/02)
-
- The synthesis of β-keto lactones via cyclization of β-keto ester dianions or the cyclization of Meldrum's acid derivatives
-
Two new methods to synthesize macrocyclic β-keto lactones have been developed.The first involves the synthesis of ω-halo-β-keto esters and an intramolecular alkylation of the dianions to these compounds.The reaction is complicated by elimination in the small and medium ring systems and by difficulties in purifying the final products.However, it is possible to obtain modest yields of the desired β-keto lactones.This procedure was used to synthesize the 25- and 27-membered ring β-hydroxy lactones that are the constituents of termite defense compounds.The second method involves the thermolysis of acylated Meldrum's acid derivatives, which leads directly to β-keto lactones.This process gives modest yields of macrocyclic systems and good yield of the unsubstituted 3-oxopentan-5-olide (25) .The 14-membered macrocyclic β-keto lactone 9j has a complex 1H NMR spectrum, which has been interpreted in terms of multiple conformations.The temperature dependence of the NMR spectrum of 9j is consistent with entropic, rather than enthalpic, control of the equilibrium.Quasiharmonic entropy calculations are consistent with this model.
- Lermer, Leonard,Neeland, Edward G.,Ounsworth, James P.,Sims, Russell J.,Tischler, Samuel A.,Weiler, Larry
-
p. 1427 - 1445
(2007/10/02)
-
- Convenient Asymmetric Synthesis of 3(S)-3--5-hydroxypyrrolidon-2-one, a Useful Synthon for the Thienamycin-like γ-Lactam
-
Chiral 3-substituted 5-hydroxypyrrolidin-2-one 12, useful for the synthesis of thienamycin-like γ-lactam, was successfully synthesised by utilising highly diastereoselective alkylation with the tin(II) enolate of 7 onto acetaldehyde, ammonolysis of the resultant amide 9, and oxidative cyclisation of 11.
- Nagao, Yoshimitsu,Matsunaga, Hiroshi,Kumagai, Toshio,Inoue, Yoshinori
-
p. 436 - 437
(2007/10/02)
-