Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 20
Filter
Add more filters










Publication year range
1.
J Org Chem ; 88(17): 12776-12782, 2023 Sep 01.
Article in English | MEDLINE | ID: mdl-37614008

ABSTRACT

In this study, we propose heavy-metal-free reductive coupling of arylacetylenes with benzothiazole sulfones. The reactions of alkyl or benzylic benzothiazole sulfones with arylacetylenes are successfully performed in the presence of Hantzsch esters and K2CO3 under visible-light irradiation to afford 1,2-disubstituted alkenes in moderate to good yields, with Z-isomer as the major product. The utility of this protocol is expanded to α-deuterative coupling using a deuterated Hantzsch ester, furnishing the corresponding alkenes with high deuterium incorporation.

2.
Chem Commun (Camb) ; 57(77): 9858-9861, 2021 Sep 28.
Article in English | MEDLINE | ID: mdl-34490858

ABSTRACT

A visible-light-induced desulfonylative Giese-type reaction has been developed. Essential to the success is the employment of Hantzsch ester to activate benzothiazole sulfones without any heavy-metal additives. Not only benzylic benzothiazole sulfones but also alkyl ones were viable substrates and reacted with electron-deficient alkenes and a propiol amide.

3.
Beilstein J Org Chem ; 16: 2769-2775, 2020.
Article in English | MEDLINE | ID: mdl-33224303

ABSTRACT

New synthetic methods for spirolactams bearing an α-methylene-γ-butyrolactone or its analogous methylene-lactam have been developed. The allylation of γ-phenylthio-functionalized γ-lactams with 2-(acetoxy)methyl acrylamides was accomplished by using 2.5 equivalents of NaH to give the corresponding adducts in excellent yields. The remaining phenylthio group was substituted with a hydroxy group by treatment with CuBr, and the resulting γ-hydroxyamides were cyclized under acidic conditions to afford the corresponding methylene-lactam-fused spirolactams in high yields. On the other hand, methylene-lactone-fused spirolactams could be delivered from the allyl adducts in high yields through a sequential N-Boc protection/desulfinative lactonization.

4.
J Org Chem ; 84(19): 12532-12541, 2019 10 04.
Article in English | MEDLINE | ID: mdl-31525925

ABSTRACT

Pharmaceutically attractive methylene lactone- and methylene lactam-based spiro compounds have been synthesized by employing amido-functionalized γ-hydroxylactam as a common intermediate. Development of a new route for bifurcated synthesis of two types of N,O-spiro compounds was accomplished by treatment of the intermediate under acidic conditions, leading to potent cytotoxic methylene lactone-based spiro compounds. New methylene lactam-based N,N-spiro compounds could be delivered via N-tert-butyloxycarbonyl protection of the terminal amide moiety of the intermediate followed by lactam cyclization under basic conditions.


Subject(s)
Antineoplastic Agents/pharmacology , Lactams/pharmacology , Lactones/pharmacology , Spiro Compounds/pharmacology , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Cell Line, Tumor , Cell Proliferation/drug effects , Crystallography, X-Ray , Drug Screening Assays, Antitumor , Lactams/chemistry , Lactones/chemistry , Mice , Models, Molecular , Molecular Structure , Spiro Compounds/chemical synthesis , Spiro Compounds/chemistry
5.
Langmuir ; 35(30): 9740-9746, 2019 Jul 30.
Article in English | MEDLINE | ID: mdl-31272152

ABSTRACT

We have developed a new photon upconversion (UC) system utilizing a new amphiphilic sensitizer 1a that comprises a hydrophilic ruthenium complex and a lipophilic bisanthracene appendage. At concentrations higher than 5 µM in toluene, the sensitizer 1a formed a reverse micellar assembly which facilitated the triplet sensitization of 9,10-diphenylanthracene (DPA) more efficiently than homogeneously dispersed solutions to enhance the UC efficiency up to 38.2%. The Stern-Volmer analyses revealed the stepwise triplet-triplet energy transfers (TTET): (1) intramicellar energy transfer from the ruthenium core to the bisanthracene surface and (2) diffusion-dependent energy transfer from the surface to DPA. On these bases, it can be assumed that the reverse micellar assemblies accelerate the former TTET process to enhance the UC efficiency.

6.
Org Biomol Chem ; 17(10): 2614-2618, 2019 03 06.
Article in English | MEDLINE | ID: mdl-30762059

ABSTRACT

The catalytic enantioselective propargylation of aldehydes with newly prepared stannyl allenyl amides is described. The reaction has been accomplished by using catalytic amounts of indium chloride, zinc chloride, and a chiral BINOL derivative, affording amide-functionalized homopropargyl alcohols in excellent yields and enantioselectivities.

7.
J Org Chem ; 83(2): 624-631, 2018 01 19.
Article in English | MEDLINE | ID: mdl-29286661

ABSTRACT

Practical synthesis of bay-monofunctionalized perylene dyes has been developed based on controllable NBS bromination of tetrabenzyl perylene-3,4,9,10-tetracarboxylate. The ability to perform the convenient and high-yielding synthesis highlights the potential utility of our multifunctional approach to access a diverse range of new perylene systems.

8.
Org Biomol Chem ; 15(2): 320-323, 2017 Jan 04.
Article in English | MEDLINE | ID: mdl-27910978

ABSTRACT

A highly enantioselective amide allylation of α-iminoamides has been achieved using catalytic amounts of InCl3, ZnCl2 and a BINOL derivative. This reaction allowed facile access to a variety of amide functionalised α-methylene-γ-butyrolactams in excellent yields with high enantioselectivities.


Subject(s)
Allyl Compounds/chemical synthesis , Amides/chemistry , Indium/chemistry , Lactams/chemical synthesis , Allyl Compounds/chemistry , Catalysis , Lactams/chemistry , Molecular Structure , Stereoisomerism
9.
Org Lett ; 17(23): 5846-9, 2015 Dec 04.
Article in English | MEDLINE | ID: mdl-26580495

ABSTRACT

A novel and facile synthesis of azaspiro-γ-lactones with a methylene-lactam framework from N-carbonyl imides is described. Mechanistic investigations provide evidence for a two-step reaction process involving ZnCl(2)-promoted addition of ß-amido allylindium species followed by an unexpectedly molecular-sieves-mediated ring opening-reclosure concomitantly with the loss of an N-carbonyl unit.


Subject(s)
Amides/chemistry , Aza Compounds/chemical synthesis , Imides/chemistry , Indium/chemistry , Lactams/chemistry , Lactones/chemical synthesis , Spiro Compounds/chemical synthesis , Aza Compounds/chemistry , Catalysis , Chlorides/chemistry , Lactones/chemistry , Molecular Structure , Spiro Compounds/chemistry , Zinc Compounds/chemistry
10.
Org Biomol Chem ; 12(39): 7686-9, 2014 Oct 21.
Article in English | MEDLINE | ID: mdl-25167094

ABSTRACT

This communication reports a significant breakthrough on the novel catalytic amide allylation to the acyclic α-ketoester systems, achieving satisfactorily high yields and extremely high levels of the asymmetric induction to allow for highly enantioselective synthesis of ester functionalised α-methylene-γ-butyrolactones.


Subject(s)
4-Butyrolactone/analogs & derivatives , Amides/chemistry , 4-Butyrolactone/chemical synthesis , 4-Butyrolactone/chemistry , Catalysis , Chemistry Techniques, Synthetic , Esters , Stereoisomerism , Substrate Specificity
11.
Chemistry ; 20(35): 11091-100, 2014 Aug 25.
Article in English | MEDLINE | ID: mdl-25049083

ABSTRACT

This article is a full account of the work exploring the potential utility of catalytic enantioselective amide allylation of various isatins using indium-based chiral catalysts. A survey of various isatin substrates and NH-containing stannylated reagents revealed that the reaction has a remarkably wide scope to result in extremely high yields and enantioselectivities (up to >99 %, 99 % ee) of variously substituted homoallylic alcohols. Several mechanistic investigations demonstrated that the substrate-reagent hydrogen-bond interaction plays a critical role in the formation of the key transition states to result in enhanced catalytic reaction. The success of this approach allowed convenient access to chiral 2-oxindoles spiro-fused to the α-methylene-γ-butyrolactone functionality and their halogenated derivatives in almost enantiopure forms, thus highlighting the general utility of this synthetic method to deliver a large variety of antineoplastic drug candidates and pharmaceutically meaningful compounds.


Subject(s)
4-Butyrolactone/analogs & derivatives , Amides/chemistry , Indoles/chemistry , Isatin/chemistry , Spiro Compounds/chemistry , 4-Butyrolactone/chemistry , Catalysis , Models, Molecular , Molecular Structure , Oxindoles , Stereoisomerism
12.
Angew Chem Int Ed Engl ; 53(16): 4213-6, 2014 Apr 14.
Article in English | MEDLINE | ID: mdl-24623596

ABSTRACT

A highly stereocontrolled, convergent total synthesis of kendomycin [(-)-TAN2162], an ansa-macrocyclic antibiotic, is reported. The key of the strategy is an unprecedented Tsuji-Trost macrocyclic etherification, followed by a transannular Claisen rearrangement to construct the 18-membered carbocyclic framework. The oxa-six- and five-membered rings were also stereoselectively constructed respectively by a cascade oxidative cyclization at an unfunctionalized benzylic position and using a one-pot epoxidation/5-exo-tet epoxide opening.


Subject(s)
Anti-Bacterial Agents/chemical synthesis , Ethers/chemistry , Rifabutin/analogs & derivatives , Molecular Structure , Oxidation-Reduction , Rifabutin/chemical synthesis , Rifabutin/chemistry , Stereoisomerism
13.
Org Lett ; 15(24): 6182-5, 2013 Dec 20.
Article in English | MEDLINE | ID: mdl-24224753

ABSTRACT

A remarkably effective method allowing an extremely high enantioselective synthesis of the spiro-fused 2-oxindole/α-methylene-γ-butyrolactones is described. The key strategy lies in the use of indium-catalyzed asymmetric amide allylation of N-methyl isatin with functionalized allylstannanes, which can lead to the antineoplastic spirocyclic lactones in almost enantiopure forms.


Subject(s)
4-Butyrolactone/analogs & derivatives , Amides/chemistry , Indoles/chemical synthesis , Isatin/chemistry , Organometallic Compounds/chemistry , Spiro Compounds/chemical synthesis , 4-Butyrolactone/chemical synthesis , 4-Butyrolactone/chemistry , Catalysis , Indium/chemistry , Indoles/chemistry , Molecular Structure , Oxindoles , Spiro Compounds/chemistry , Stereoisomerism
14.
Nat Prod Commun ; 8(7): 889-96, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23980417

ABSTRACT

A simple and straightforward synthetic approach was developed to access a biologically important class of alpha-aminomethyl-gamma-butyrolactones via a beta-lactam synthon strategy involving successive ring-opening and lactonization processes from alpha-hydroxyethyl-substituted beta-lactams that were elaborated by SmI2-mediated reductive coupling reaction.


Subject(s)
Lactones/chemical synthesis , beta-Lactams/chemistry , 4-Butyrolactone/analogs & derivatives , Iodides/pharmacology , Lactones/chemistry , Magnetic Resonance Spectroscopy , Oxidation-Reduction , Samarium/pharmacology
15.
Nat Prod Commun ; 8(7): 1011-9, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23980437

ABSTRACT

Batzellasides A-C are C-alkylated piperidine iminosugars isolated from a sponge, Batzella sp. The first total synthesis of (+)-batzellaside B was achieved by employing a chiral pool approach starting from L-arabinose for the construction of a piperidine ring system. Subsequently, a practical second-generation synthesis was developed by utilizing a Sharpless asymmetric dihydroxylation for the preparation of the common piperidine intermediate elaborated in the first-generation synthesis. The overall yield of batzellaside B was improved to 3.3% by introducing the exocyclic C8 stereocenter via facial selective hydride addition to a linear ketone. These syntheses allowed for the determination of the absolute stereochemistry of this natural product as well as for providing precious samples, which would pave the way for further biological studies.


Subject(s)
Amino Sugars/chemical synthesis , Amino Sugars/chemistry , Models, Molecular , Molecular Conformation
16.
Beilstein J Org Chem ; 8: 1831-8, 2012.
Article in English | MEDLINE | ID: mdl-23209519

ABSTRACT

A new synthetic approach to (+)-batzellaside B from naturally abundant L-pyroglutamic acid is presented in this article. The key synthetic step involves Sharpless asymmetric dihydroxylation of an olefinic substrate functionalized with an acetoxy group to introduce two chiral centres diastereoselectively into the structure. Heterocyclic hemiaminal 4, which could be converted from the resulting product, was found to provide stereospecific access to enantiomerically enriched allylated intermediate, offering better prospects for the total synthesis of this natural product.

17.
Org Lett ; 14(19): 5142-5, 2012 Oct 05.
Article in English | MEDLINE | ID: mdl-23009150

ABSTRACT

The first total synthesis of antibacterial epicoccarine A isolated from a fungus Epicoccum sp. has been accomplished in 10 steps along with synthetic elaboration of its C5-epimer, highlighting the utility of O- to C-acyl rearrangement of a 4-O-acyltetramic acid derivative. Comparison of spectroscopic properties and specific optical rotations of the synthetic samples with those reported for authentic material has clearly indicated the unspecified absolute stereochemistry of this natural product to be 5S.


Subject(s)
Pyrrolidinones/chemical synthesis , Molecular Structure , Stereoisomerism
18.
J Org Chem ; 77(9): 4391-401, 2012 May 04.
Article in English | MEDLINE | ID: mdl-22510093

ABSTRACT

For the efficient approach to medicinally important α-branched 3-acyltetramic acids, the key reaction of O- to C- acyl rearrangement using α-amino-acid-derived 4-O-acyltetramic acids was extensively examined in the presence of various metal salts. Use of CaCl(2) or NaI dramatically changed the results in the reaction efficiency and rapidly brought about the desired α-branched 3-acyltetramic acids in markedly improved yields. We also discuss an epimerization at C5 stereocenter under the rearrangement conditions as well as the tolerance for structural variation at C3 and C5. In addition to the preceding success in the total synthesis of new cytotoxic tetramic acid, penicillenol A(1), this methodology could be also applied to the first total synthesis of penicillenol A(2).


Subject(s)
Amino Acids/chemical synthesis , Pyrrolidinones/chemical synthesis , Amino Acids/chemistry , Molecular Structure , Pyrrolidinones/chemistry , Stereoisomerism
19.
J Colloid Interface Sci ; 356(2): 536-42, 2011 Apr 15.
Article in English | MEDLINE | ID: mdl-21296360

ABSTRACT

Detailed exploratory and mechanistic investigations on spontaneous formation of dye-functionalized gold nanoparticles (GNPs) using dye-based reverse micellar systems are described in this publication. The accumulated results from spectroscopic and microscopic investigations demonstrated that water molecules confined within nanoscopic enclosure of the self-assembled reverse micelles played critical role in the redox processes of aurate ions to produce GNPs, which are assumed to have approximately constant size distributions. The resulting dye-functionalized GNPs were found to offer their absorption and fluorescence emission tunability by changing the medium polarity as well as to exhibit excellent film-forming properties to give optically homogeneous polystyrene thin films. These key findings in addition to broad applicability of the self-assembling process with a variety of dye analogues have led to a conclusion that the protocol presented here serves as a versatile synthetic method to provide a potential convenience for future development of new organic-inorganic hybrid nanomaterials.

20.
Chem Commun (Camb) ; (10): 1220-1, 2004 May 21.
Article in English | MEDLINE | ID: mdl-15136847

ABSTRACT

Synthesis of the C13-C19 C-glycoside portion of kendomycin was achieved via oxidative pyran cyclization and Claisen rearrangement to construct the fully functionalized aromatic ring.


Subject(s)
Monosaccharides/chemical synthesis , Rifabutin/analogs & derivatives , Rifabutin/chemical synthesis , Glycosides
SELECTION OF CITATIONS
SEARCH DETAIL
...