ABSTRACT
A highly efficient annulative approach towards the construction of the structurally attractive methylenecyclohexane ring was developed through a convenient 1,4-addition of 4-pentenylmagnesium bromide to 2-cyano-2-cycloalkenones followed by a Pd(II)-mediated oxidative cyclization of the resulting ω-unsaturated α-cyano ketones. Based on this newly developed protocol, polycyclic adducts bearing various ring sizes and substitutions can be prepared in moderate to high yields.
Subject(s)
Acetates/chemistry , Cyanoketone/chemistry , Cyclohexanes/chemistry , Organometallic Compounds/chemistry , Cyclization , Methylation , Molecular Structure , Oxidation-ReductionABSTRACT
Under catalysis with ZnI(2), an effective annulation process of ω-silylacetylenic α-cyano ketones, leading to the formation of various bicyclic frameworks characterized with a TMS-containing methylenecyclopentane ring, has been developed.
Subject(s)
Alkanes/chemical synthesis , Alkynes/chemistry , Cyanides/chemistry , Trimethylsilyl Compounds/chemistry , Cyclization , Ketones , Molecular StructureABSTRACT
Starting from 4-methylcyclohexanone (7), a concise total synthesis of the pinguisane-type sesquiterpenoid acutifolone A, in racemic form, has been accomplished in 14 steps with an overall yield of 14.5%.
Subject(s)
Cyclohexanes/chemistry , Diazonium Compounds/chemistry , Oxygen/chemistry , Cyclization , Molecular Structure , StereoisomerismABSTRACT
Polyene cyclization of the titled compounds under catalysis with AlCl(3)/SnCl(4) gave rise to the corresponding polycyclic products, many of which were structurally highly unexpected, and thus, individual X-ray analysis was required to finalize the structural identification. Mechanistically, an unusual 1,2-hydride shift is proposed to elucidate the product formation.
Subject(s)
Cyclohexanones/chemistry , Polycyclic Compounds/chemical synthesis , Polyenes/chemistry , Aluminum Chloride , Aluminum Compounds/chemistry , Catalysis , Chlorides/chemistry , Crystallography, X-Ray , Cyclization , Molecular Structure , Polycyclic Compounds/chemistry , Stereoisomerism , Tin Compounds/chemistryABSTRACT
The first total syntheses of (+/-)-montanin A and (+/-)-teuscorolide have been achieved from an advanced precursor previously developed via a Diels-Alder strategy; in the synthetic sequence, the synthesis of montanin A was first accomplished in 8 steps, from which teuscorolide was readily achieved in 2 steps by using a novel furan oxidative cyclization-retro-cyclization process as a key operation.
Subject(s)
Furans/chemical synthesis , Pentanols/chemistry , Spiro Compounds/chemical synthesis , Cyclization , Furans/chemistry , Molecular Conformation , Spiro Compounds/chemistry , StereoisomerismABSTRACT
Polyene cyclization of compounds 3 and 4 under catalysis with AlCl3 and/or SnCl4 gave rise to complex bicyclic products 8 and 9, structures of which were highly unexpected, and X-ray analyses were invoked for unambiguously structural identification. Mechanistically, a tandem sigma-bond rearrangement process, including an unusual through-space 1,5-hydride or 1,3-alkyl shift as a key operation, is proposed.
Subject(s)
Alkenes/chemistry , Ketones/chemistry , Catalysis , Cinnamates/chemistry , Cyclization , Molecular Structure , Stereoisomerism , Zinc/chemistryABSTRACT
Starting from (-)-beta-pinene, the first total synthesis of xenitorins B and C has been accomplished, which also allowed the assignment of their absolute configuration.
Subject(s)
Sesquiterpenes/chemistry , Sesquiterpenes/chemical synthesis , Molecular Conformation , TemperatureABSTRACT
[reaction: see text] Starting from 4,4-dimethyl-2-cyclohexenone, an efficient total synthesis of ricciocarpin A (1) in natural form has been accomplished.
Subject(s)
Furans/chemical synthesis , StereoisomerismABSTRACT
The absence of effective vaccines for most viral infections highlights an urgent necessity for the design and development of effective antiviral drugs. Due to the advancement in virology since the late 1980s, several key events in the viral life cycle have been well delineated and a number of molecular targets have been validated, culminating in the emergence of many new antiviral drugs in recent years. Inhibitors against enteroviruses and rhinoviruses, responsible for about half of the human common colds, are currently under active investigation. Agents targeted at either viral protein 1 (VP1), a relatively conserved capsid structure mediating viral adsorption/uncoating process, or 3C protease, which is highly conserved among different serotypes and essential for viral replication, are of great potential to become antipicornavirus drugs.
Subject(s)
Antiviral Agents/pharmacology , Capsid/metabolism , Enterovirus/drug effects , Protease Inhibitors/pharmacology , Rhinovirus/drug effects , Antiviral Agents/metabolism , Protease Inhibitors/metabolism , Protein BindingABSTRACT
A highly efficient methylenecyclopentane annulation process has been developed based on the Pd(II)-mediated oxidative cyclization of omega-unsaturated alpha-cyano ketones, readily accessed via the Michael addition of 3-butenylmagnesium bromide with 2-cyano-2-cycloalkenones.
ABSTRACT
Enone phosphonates 1 and 2 were found to be excellent dienophiles for the Diels-Alder reaction, giving phosphonate-containing polycycles, and the phosphonate group of the resulting adducts facilitated both the installation of an angular alkyl group via a reductive alkylation process and the regioselective generation of a ring junction double bond via an intramolecular Wadsworth-Horner-Emmons reaction.
