A modular synthesis of the lamellarins: total synthesis of lamellarin G trimethyl ether

A modular synthesis of the lamellarin family of natural products has been developed that is based on the application of three iterative halogenation/cross-coupling reaction sequences. The ability to halogenate the pyrrole core in a regioselective fashion, even in the presence of highly electron-rich aryl substituents, has been established. The compatibility of Suzuki coupling conditions with free alcohols and phenols in the boronic acids has been employed to reduce the number of protection/deprotection steps. Indeed, the presence of a free phenol on boronic acid 3 has been determined to be critical for the successful final coupling in route to lamellarin G trimethyl ether, since protected versions fail to undergo coupling.     

An efficient strategy for the synthesis of endocyclic enol ethers and its application to the synthesis of spiroacetals

An efficient strategy for the synthesis of endocyclic enol ethers based on a Suzuki-Miyaura coupling/ring-closing metathesis sequence has been developed. The strategy has successfully been applied to the synthesis of spiroacetals, including cytotoxic marine metabolites attenols A and B.     

Peculiarities of the synthesis of cage-like metallosiloxanes

The synthesis of individual Ni-, Mn-, and Na-containing cage-like organometallosiloxanes has been performed. A possible mechanism of the formation of stable metallosiloxane frameworksvia a transition complex and coordinately bound ion pairs has been proposed. Both monometallic and bimetallic organometallosiloxanes containing only atoms of a transition metal or two different (transition and non-transition) metals, respectively, have been prepared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 957–961, May, 1993.     

Towards the synthesis of perfluoroalkylated derivatives of Xantphos

An analogue of Xantphos incorporating four perfluoroalkyl groups has been prepared and successfully used as a ligand in the rhodium-catalysed hydroformylation of 1-octene in toluene. A number of perfluoroalkylated xanthene backbones have also been synthesised, but their conversion into preferentially perfluorocarbon solvent soluble Xantphos-type ligands, suitable for catalysis in fluorocarbon solvents, has not been successful.     

Studies toward the total synthesis of azaspiracids: synthesis of the FGHI ring domain

Synthesis of the FGHI ring domain of azaspiracids, the causative agents for a new type of shellfish poisoning, azaspiracid poisoning (AZP), has been achieved. The synthesis features dithiane anion-epoxide coupling for convergent fragment assembly.     

New convenient synthesis of iridol. An approach to the synthesis of ubiquinones

A strategy for the synthesis of ubiquinones, in which iridol is the key intermediate, has been developed, together with a new convenient synthesis of iridol (2,3-dimethoxy-5-methylphenol) starting from the easily available 4-methylphenol and using mild conditions and friendly and high-yielding reactions.     

A metathesis-based approach to the synthesis of furans

The enol ether-olefin ring-closing metathesis reaction has been employed to generate 2,3-dihydrofurans that are equipped with a leaving group. These substrates are at the correct oxidation state to undergo an acid-catalyzed aromatization, and this strategy has been utilized to provide a mild and rapid route (four steps) to a range of novel 2,5-disubstituted furans. [reaction: see text]     

Enantioselective methodologies for the synthesis of spiro compounds

The enantioselective synthesis of spirocycles has been a long time pursued dream for organic chemists. Since the first pioneering efforts of Tamao and coworkers in the enantioselective construction of spirosilanes, many efforts have been devoted to the development of new and promising asymmetric methodologies. Remarkably, with the advent of organocatalysis the number of methodologies has been highly increased. The aim of this tutorial review is to summarize the last trends and developments reported in the literature in the enantioselective synthesis of spirocompounds.     

Studies toward the total synthesis of nagelamide K

A stereocontrolled strategy toward the synthesis of nagelamide K has been developed. The dimeric imidazole acrylate, diimidazolidenesuccinate, was constructed as a synthetic precursor by a Ni-catalyzed coupling reaction; the microwave-promoted intramolecular aza-Michael addition afforded the imidazo[1,5-a]pyridine core structure of nagelamide K in high stereoselectivity. A detaurine-dediamino analogue of nagelamide K has been prepared.     

Model studies for the synthesis of galbonolide B

The construction of the fourteen membered ring present in galbonolide B 1 is reported. The 10,11-diene system present in the southern portion of has been constructed using an ester enolate rearrangement/silicon mediated fragmentation cascade, whilst the macrocycle has been synthesised following a Johnson rearrangement/mercury assisted ring closure protocol.     

A concise and stereoselective synthesis of the A-ring fragment of the gambieric acids

The A-ring fragment of the gambieric acids has been prepared by a short and efficient route. The key 3(2H)-furanone intermediate has been obtained by [2,3] rearrangement of an allylic oxonium ylide generated from intramolecular reaction of a crotyl ether with a copper carbenoid. A single stereogenic center has been set by using a chiral pool starting material and the other three have been established by using highly diastereoselective substrate-controlled transformations. [reaction--see text]     

Studies towards the synthesis of the northern polyene of viridenomycin and synthesis of Z-double bond analogues

Viridenomycin is a structurally challenging, potentially biologically valuable molecule which has yet to succumb to total synthesis. Its instability, perhaps particularly associated with the northern polyene may contribute to the difficulties of piecing this molecule together. The synthesis of northern polyene models, including potentially stabilised analogues incorporating benzene rings as Z-alkene replacements, have been prepared using an efficient series of cross-coupling reactions. The resulting polyenes and polyene surrogates have been converted into tetraene ester and amide models of the viridenomycin system. These analogues have sufficient stability compared with the unsubstituted northern polyene analogue to be viable for future developing a strategy for the construction of viridenomycin and analogues.     

A rapid and convergent synthesis of the integrastatin core

The tetracyclic core of the integrastatin natural products has been prepared in a convergent and rapid manner. Our strategy relies upon a palladium(II)-catalyzed oxidative cyclization to form the central [3.3.1]-dioxabicycle of the natural product core. Overall, the core has been completed in only 4 linear steps from known compounds.     

Hexabrominated porphyrins in the synthesis of fluorene-containing polyphenols

A new strategy for the synthesis of fluorene-containing polyphenols of porphyrin series by the Suzuki–Miyaura reaction of hexabromoporphyrin and monoboryl derivative of substituted fluorene has been proposed. Several sequential chemical transformations of the prepared porphyrin allowed preparation of polyphenol derivative of the noted compound. Similar polyphenol has been used as a basis for the design of positive photoresists for nanolithography with 13.5-nm exposing radiation, which can produce topological structures with resolution 22–16 nm.     

Total synthesis of ingenol

A total synthesis of the biologically important diterpene ingenol has been completed. Ring-closing olefin metathesis was used to construct the strained "inside-outside" tetracyclic skeleton, and a series of diastereoselective reactions were employed to complete the synthesis. Another naturally occurring ingenane, 20-deoxyingenol, has also been prepared.     

Tandem annulation strategy for the convergent synthesis of benzonaphthopyranones: total synthesis of chartarin and O-methylhayumicinone

A Hauser-initiated tandem annulation has been developed for the rapid regiospecific synthesis of benzonaphthopyranones via formation of two rings in one-pot operation. This strategy has been generalized with benzonaphthopyranones 26, 29, 32, and 35. It has also been employed in a short synthesis of chartarin (3) and O-methylhayumicinone (67).     

On the synthesis of chlorine pentafluoride

The reaction between chlorine trifluoride and elemental fluorine was studied in order to find the optimal reaction conditions for the synthesis of chlorine pantafluoride. It has been found that nickel difluoride is a very effective catalyst for the mentioned reaction. The obtained results are expressed as space-time-yield of chlorine pentafluoride.     

Chemo-enzymatic synthesis of a multi-useful chiral building block molecule for the synthesis of medicinal compounds

Optical resolution of 2-methyl-2-nitrobut-3-en-1-ol has been accomplished using a "low-temperature lipase-catalyzed transesterification" carried out at -40 °C.     

Stereoselective synthesis of aryl 1,2-cis-furanosides and its application to the synthesis of the carbohydrate portion of antibiotic hygromycin A

An efficient methodology for the synthesis of aryl 1,2-cis-furanosidic linkages has been developed with 2-quinolinecarbonyl (Quin) group substituted furanose ethyl thioglycosides as glycosyl donors. The method permits a wide range of phenol acceptors to be used, thus resulting in the formation of structurally diverse phenol furanosides in good to excellent chemical yields with complete 1,2-cis anomeric selectivity. The synthetic utility of the approach has been demonstrated by concise preparation of the carbohydrate portion of antibiotic hygromycin A.     

Alkynyliodonium salts in organic synthesis. Application to the total synthesis of the tropoloisoquinoline alkaloid pareitropone

The synthesis of the tropoloisoquinoline alkaloid pareitropone has been accomplished in 14 steps from 2,3,4-trimethoxybenzoic acid. The key transformations include the generation of an alkylidenecarbene intermediate through intramolecular addition of a tosylamide anion to an alkynyliodonium salt, and the cycloaddition of that carbene to a peri positioned aromatic ring to afford a cycloheptatrienylidene product featuring the intact pareitropone skeleton.