European Journal of Organic Chemistry

α-Alkylidene-substituted δ-lactones and corresponding γ- and δ-lactams have recently been attracting much attention due to their potential utility in synthetic and medicinal chemistry. This microreview gives a compilation of synthetic approaches to these classes of compounds developed in the last decade. Particular emphasis is placed on the synthesis of nonracemic α-alkylidene lactones and lactams.

The synthesis of 3-bromo-4-fluoro- and 3-fluoro-4-iodofurans under mild conditions is reported. The key step involves electrophilic halocyclization with the use of N-halosuccinimides.

A new and flexible procedure for the synthesis of chiral azolium salts derived from (S)-pyroglutamic acid has been described. These salts were used as precursors to N-heterocyclic carbenes for the rhodium-catalyzed asymmetric transfer hydrogenation of aromatic ketones in isopropanol, giving good yields and enantioselectivities (up to 94 % yield and 90 % ee).

The enantioselective synthesis of deoxymannojirimycin is reported. The enantioselectivity is introduced by Sharpless asymmetric epoxidation, followed by an intramolecular aldolization to build the piperidine core.

o-Alkynylarenecarbaldehydes undergo oxidation with an iodine/water system via isochromenol intermediates to furnish tricarbonyl compounds in good yields.

An efficient and mild one-pot synthesis of3-alkyl(3-aryl)-2-aminoquinazolin-4(3H)-ones is reported. Starting from diversely substituted anthranilates, the successive addition of ethoxycarbonyl isothiocyanateand diverse primary amines in the presence of the coupling reagent EDCI at room temperature provided a library of 2-amino-3-alkyl(3-aryl)quinazolin-4(3H)-ones in up to 93 % yield.

The utility of the readily available asymmetric 1,3-dioxane template (in blue) in stereocontrolled intramolecular Diels–Alder reactions was studied. The 1,3,9-decatrienoate substrates gave high diastereofacial selectivities and yields, and the method was also applicable to Z-diene substrates. This approach provided an efficient asymmetric route to harringtonolide and ent-pyrrocidine.

We obtained carbon nanotubes dispersed in water by wrapping them with the cyclodextrin-modified polysaccharide curdlan (CD-CUR) to produce a composite. Adding poly(acrylic acid)-modified azobenzenes as side chains into the aqueous solution of the composite of CD-CUR and single-walled carbon nanotubes (CD-CUR/SWNT) produced a supramolecular photoresponsive hydrogel.

Suzuki coupling and a click reaction allows the construction of rigid, water-soluble bis- and tetrakis-Zn^II–cyclen complexes. The complexes serve as efficient fluorescent “turn-on” chemosensors for genetically encodable oligoaspartate and glutamate sequences (D₄ and E₄ tags) and as “turn-off” sensors for pyrophosphate anions.

Access to enantiopure synthetic platforms that can generate key intermediates for salvinorin A and 20-nor-salvinorin A analogues is described.

1-Aryl/alkyl-1H-1,2,3,4-tetrazoles are synthesized from TMSN₃/CH(OEt)₃/IL-1 and TMSN₃/CH(OEt)₃/IL-2, benzazoles from RCH(OEt)₃ with IL-1 and IL-2, andquinazolinones from anthranilic acid and anthranilamide with CH(OEt)₃/IL-1.

Rhodium- and ruthenium-catalyzed cycloadditions of alkynylynamides and nitriles are the key steps in a new synthesis ofcarbolines and have been applied in the total synthesis of perlolyrine and its γ-isomer.

Lavendamycin has been synthesized by a highly convergent strategy. The key steps of this synthesis involve a ruthenium-catalyzed [2+2+2] cycloaddition of an electron-deficient nitrile to an alkynyl-ynamide to prepare the carboline scaffold, an N-ethynylation, and two palladium-catalyzed cross-coupling reactions.

Pyrrole derivatives can be efficiently arylated with aryl iodides in ionic liquids ([emim][OAc] = 1-ethyl-3-methylimidazolium acetate). The reaction for N-alkyl- and N-arylpyrroles affords 2-arylated products in good yields andwith high regioselectivity. The process proceeds without addition of transition metal salts and is promoted by KOAc, which makes it remarkably compatible with a broad variety of functional groups.

The Lewis acid-mediated ring-opening rearrangement of bicyclo[4.4.1.0]-undecane-1-one and related cyclopropyl ketones proceeds smoothly using a combination of stannous triflate [Sn(OTf)₂] and Ac₂O.

Two new chromones, phomochromone A and B (1 and 2), and one new natural cyclopentenone, phomotenone (3), have been isolated from the endophytic fungusPhomopsis sp. through a bioassay-guidedprocedure. The absolute configurations of compounds 1–3 were assigned by TD-DFT CD calculations. Compounds 1–3 showed good antifungal, antibacterial, and antialgal activities.

o-(6′-Nitrocyclohex-3′-en-1′-yl)phenol and tetrahydro-6H-benzo[c]chromen-6-ol derivatives were synthesized starting fromsalicyladehyes in three steps. Solid catalysts (PS-TDB and TBAF on silica) and solvent-free conditions were generally used.