Application of intramolecular Dötz reaction to the synthesis of ansa-compounds: concise synthesis of arnebinol

Fischer carbene complexes having long alkynyloxy chains regioselectively produced oxametacyclophanes via the intramolecular Dötz reaction. The utility of this reaction was demonstrated in the synthesis of arnebinol, an ansa-type terpenoid, from geranyl acetate in six steps.     

Studies towards the total synthesis of Sch 56036; isoquinolinone synthesis and the synthesis of phenanthrenes

The isoquinolinone hemisphere of Sch 56036 has been prepared using a modified Pomeranz-Fritsch reaction and the synthesis of the phenanthrene core has been modelled via a Suzuki coupling and subsequent ring closing metathesis.     

A facile approach to the synthesis of securinega alkaloids: stereoselective total synthesis of (−)-allonorsecurinine

A concise stereoselective total synthesis of alkaloid (−)-allonorsecurinine is described utilizing classical reactions such as Grignard, Aldol and Horner-Wittig reactions as the key steps.     

Horseradish peroxidase catalyzed oxidative cross-coupling reactions: the synthesis of ‘unnatural’ dihydrobenzofuran lignans

The possibility to afford by a biomimetic reaction ‘unnatural’ products, which could offer a better bioactivity profile than natural analogues, is outlined and the first applications to the synthesis of lignans and related compounds have been reported. Here we describe the synthesis of new heterodimers, having a phenylcoumaran skeleton, by horseradish peroxidase catalyzed cross-coupling reactions of methyl esters of substituted hydroxycinnamic acids.     

Ring-closing iodoamination of homoallylic amines for the synthesis of polysubstituted pyrrolidines: application to the asymmetric synthesis of (−)-codonopsinine

Ring-closing iodoamination of (E)-configured, N-α-methyl-p-methoxybenzyl protected homoallylic amines upon treatment with I₂ and NaHCO₃ in MeCN occurs with concomitant loss of the N-α-methyl-p-methoxybenzyl group to give 3-iodopyrrolidines in >99:1 dr. This transformation was used as one of the key steps in the total asymmetric synthesis of (?)-codonopsinine, which was achieved in seven steps (from commercially available tert-butyl crotonate) in 5% overall yield and >99:1 dr.     

Microwave‐assisted synthesis of disulfides using tetrathiomolybdate: A step toward greener synthesis

An eco‐friendly, efficient, and rapid synthetic procedure for disulfides using benzyl triethyl ammonium tetrathiomolybdate through microwave irradiation of solid support adsorbed reactants is reported. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:373–376, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21025     

Radical cyclization studies directed toward the synthesis of BMS-200475 ‘entecavir’: the carbocyclic core

Two routes are presented for the conversion of d-diacetone glucose (5a) into a protected carbocyclic core of BMS-200475 (Entecavir). The reduction of two terminal epoxides with Cp₂TiCl to form carbon radicals and their cyclizations with a terminal acetylene and an α,β-unsaturated ester lead ultimately to allylic alcohol 11a, a candidate for Mitsunobu coupling with guanine.     

Two isolated intermediates of the Tröger's base: synthesis and mechanism

By controlling the amount of catalyst 1-methyl-3-(2-(sulfooxy)ethyl)-1H-imidazol-3-ium chloride, two new intermediates of Tröger's bases (11, 1,6-dimethyl-3-(4-methylphenyl)-1,4-dihydroquinazolin-3-ium tetrafluoroborate and 12, 8-methyl-2,5-bis-(4-methylphenyl)-3,5,6,7-tetrahydropyrimido[5,6,1-ij]quinazoline-2-ium tetrafluoroborate) were simply obtained from the one-pot reaction of aromatic amine and formaldehyde in ionic liquid at ambient temperature. These results support the mechanism for Tröger's base formation supposed by Fernando Coelho and co-workers. However, the crystal structure of 12 and correlative quantum chemistry calculation results are not reconciled with their report.     

Exploiting the Maitland-Japp reaction: a synthesis of (±)-centrolobine

Application of our one-pot, three-component variation of the Maitland-Japp reaction has led to the formation of a tetrahydropyran-4-one, which was converted in three steps to the antiparasitic and antibiotic natural product (±) centrolobine.     

Efficient synthesis of 2,4-disubstituted thiazoles using ionic liquid under ambient conditions: a practical approach towards the synthesis of Fanetizole

A highly efficient and rapid synthesis of 2-amino-4-arylthiazoles and 2-methyl-4-arylthiazole from α-bromoketone and thiourea/thioamide is described using room temperature ionic liquid at ambient conditions. The method is simple, rapid and practical, generating thiazole derivatives in excellent isolated yields. This protocol is utilized for a commercially feasible synthesis of an anti-inflammatory agent, Fanetizole.     

One-step reductive amidation of nitro arenes: application in the synthesis of Acetaminophen™

A novel thioacetate mediated one-step reductive acetamidation of aryl nitro compounds was developed and applied to an efficient synthesis of acetaminophen. The reaction also proceeds well without a solvent in the presence of a catalytic amount of surfactant.     

Dibromomethane as one-carbon source in organic synthesis: total synthesis of (±)-canadensolide

A diastereoselective total synthesis of (±)-canadensolide is described. The key step is to introduce the α-methylene group by the ozonolysis of mono-substituted alkenes followed by reaction with a preheated mixture of CH₂Br₂-Et₂NH.     

The Pauson-Khand reaction as a new entry to the synthesis of bridged bicyclic heterocycles: application to the enantioselective total synthesis of (−)-alstonerine

The first application of the Pauson-Khand reaction (PKR) to the synthesis of azabridged bicyclic structures is described. Compounds containing azabicyclo[3.3.1]nonane and azabicyclo[3.2.1]octane rings fused to cyclopentenones were efficiently constructed via the PKR of cis-2,6-disubstituted N-acyl piperidine enyne substrates, many of which can be readily prepared from 4-methoxypyridine in a few steps. Moreover, the PKR of cis-2,6-disubstituted piperazine enynes allowed the preparation of diazabicyclo[3.3.1]nonanes fused to cyclopentenones. This new strategy for the synthesis of azabridged bicyclic frameworks was exploited as a key step in a concise, enantioselective total synthesis of the macroline alkaloid (−)-alstonerine.     

Total synthesis of apoptolidin: completion of the synthesis and analogue synthesis and evaluation

The total synthesis of apoptolidin (1) is reported together with the design, synthesis, and biological evaluation of a number of analogues. The assembly of key fragments 6 and 7 to vinyl iodide 3 via dithiane coupling technology was supplemented by a second generation route to this advanced intermediate involving a Horner-Wadsworth-Emmons coupling of fragments 22 and 25. The final stages of the synthesis featured a Stille coupling between vinyl iodide 3 and vinylstannane 2, a Yamaguchi lactonization, a number of glycosidations, and final deprotection. The developed synthetic technology was applied to the construction of several analogues including 74, 75, and 77 which exhibit significant bioactivity against tumor cells.     

Allenyl‐β‐lactams: versatile scaffolds for the synthesis of heterocycles

The hybrid allenic β‐lactam moiety represents an excellent building block for carbo‐ and heterocyclization reactions, affording a large number of cyclic structures containing different sized skeletons in a single step. This strategy has been studied under thermal and radical‐induced conditions. More recently, the use of transition‐metal catalysis has been introduced as an alternative that relies on the activation of the allenic component. On the other hand, the intramolecular version has attracted much attention as a strategy for the synthesis of bi‐ and tricyclic compounds in a regio‐ and stereoselective manner. This overview focuses on the most recently developed cyclizations on 2‐azetidinone‐tethered allenes along with remarkable early works accounting for the mechanism, as well as for the regio‐ and diastereoselectivities of the cyclizations. DOI 10.1002/tcr.201100011     

Towards the synthesis of prevezol C: total enantioselective synthesis of (−)-2-epi-prevezol C

(−)-2-epi-Prevezol C was readily accessed from the chirons (−)- and (+)-limonene oxide in a total of nine steps and in 24% yield. This efficient enantioselective synthesis of this complex product utilises a highly stereoconvergent, substrate-controlled allylic alkylation strategy to assemble rapidly the unprecedented diterpene core.