A short and efficient enantioselective route to a key intermediate for the total synthesis of forskolin

A simple route for the enantioselective synthesis of key intermediates (11 and 12) for the total synthesis of forskolin has been developed starting from acid 6 and (S)-alcohol 5. The latter is prepared by enantioselective catalytic CBS reduction of dienone 3, and is converted by an intramolecular Diels-Alder reaction to tricyclic lactone 9.     

Palladium-catalyzed synthesis of aryl ketones by coupling of aryl bromides with an acyl anion equivalent

Palladium-catalyzed couplings of aryl bromides with N-tert-butylhydrazones as acyl anion equivalents to form aryl ketones are reported. The coupling process occurs at the C-position of hydrazones to form N-tert-butyl azo compounds. Isomerization of these azo compounds to the corresponding hydrazones, followed by hydrolysis, gave the desired mixed alkyl aryl ketones. The selectivity of C- versus N-arylation was strongly influenced by the substituent on nitrogen. Arylation at carbon occurred with N-tert-butylhydrazones, whereas N-arylation occurred with N-arylhydrazones. The arylation of hydrazones containing primary and secondary alkyl groups, as well as aryl groups, gave the desired ketones in good yields after hydrolysis. Functional groups on the aromatic ring, such as alkoxy, cyano, trifluoromethyl, carboalkoxy, carbamoyl, and keto groups, were tolerated. This reaction likely occurs by C-C bond-forming reductive elimination from an intermediate containing an eta1-diazaallyl ligand.     

A short route to the synthesis of pyrroloacridines via Ullmann-Goldberg condensation

A concise method for the preparation of pyrroloacridines was reported via CuI mediated Ullmann-Goldberg condensation of 5-amino-2-methylindoles and o-halobenzoic acid derivatives followed by cyclization with POCl₃.     

A short and concise route to total synthesis of Dendrodolide L

A short and efficient method for the stereoselective synthesis of Dendrodolide L has been developed from inexpensive and commercially available starting material. This convergent synthesis utilizes Jacobsen kinetic resolution, regioselective ring-opening of epoxide and Yamaguchi macrolactonization as key steps.     

New ylide anions. A vinyl anion equivalent for substituted fumarate esters

A new type of ylide anion is reported which upon alkylation and elimination of triphenylphosphine serves as a vinyl anion equivalent.     

A novel route to aldehydic enol ethers and enamines

Base-promoted reaction of dimethyl diazomethylphosphonate ($\text{1}$) with dialkyl and cyclic ketones in the presence of alcohols and of amines affords aldehydic enol ethers and enamines, respectively.     

A regiospecific and stereospecific route to enol carbonates and carbamates: closer look at a “naked anion”

A fluoride ion catalyzed reaction which affords the title compounds in good yield from enol silyl ethers is described.     

Application of the chiral acyl anion equivalent,trans-1,3-dithiane 1,3-dioxide,to an asymmetric synthesis of (R)-salbutamol

An enantioselective synthesis of (R)-salbutamol has been carried out using the chiral, C2 symmetric acyl anion equivalent, (1R,3R)-1,3-dithiane 1,3-dioxide, which undergoes addition to an aromatic aldehyde with very high stereocontrol at 0 degrees C. Pummerer reaction and work-up with lithium ethanethiolate generated the alpha-hydroxy thiolester in high yield and further transformations led to the target compound with high enantiomeric excess.     

Acetoxy Meldrum's acid: a versatile acyl anion equivalent in the Pd-catalyzed asymmetric allylic alkylation

Acetoxy Meldrum's acid can serve as a versatile acyl anion equivalent in the Pd-catalyzed asymmetric allylic alkylation. The reaction of this nucleophile with various meso and racemic electrophiles afforded alkylated products in high yields and enantiopurities. These enantioenriched products are versatile intermediates that can be further functionalized using nitrogen- and oxygen-centered nucleophiles, affording versatile scaffolds for the synthesis of nucleoside analogues. These scaffolds were used to complete formal syntheses of the anti-HIV drugs carbovir, abacavir, and the antibiotic aristeromycin.     

Enantioselective route to a key intermediate in the total synthesis of forskolin

An enantioselective route for the total synthesis of forskolin, a potent activator of adenylate cyclase, has been developed which is based on reduction of dienone 3 to the (S)-alcohol 4 and conversion in two steps to tricyclic lactone 9, obtained in optically pure form simply by recrystallization.     

A direct route to angularly substituted hydrindanes. Formal synthesis of bakkenolide-A and synthesis of an advanced intermediate to umbellactal

A direct route for the synthesis of highly functionalized angularly substituted hydrindanes has been developed. The key step involves RO-RCM of an appropriately functionalized norbornene derivative. The hydrindane derivative obtained in this way has been used to accomplish a formal synthesis of bakkenolide-A. This protocol has also been extended for the synthesis of an advanced intermediate to the synthesis of the diterpene umbellactal.     

A short synthetic route to the calystegine alkaloids

An efficient strategy is described for the synthesis of enantiopure calystegine alkaloids. The key step employs a zinc-mediated fragmentation of benzyl-protected methyl 6-iodo-glycosides followed by in situ formation of the benzyl imine and Barbier-type allylation with zinc, magnesium, or indium metal. Stereochemistry in the pivotal allylation is controlled by the choice of the metal. The functionalized 1,8-nonadienes, thus formed, are converted into cycloheptenes by ring-closing olefin metathesis. Regioselective hydroboration and oxidation give the corresponding cycloheptanones, which are deprotected to afford the desired calystegines. Hereby, calystegine B(2), B(3), and B(4) are prepared from D-glucose, D-galactose, and D-mannose, respectively. This route constitutes the shortest synthesis of calystegine B(2) and gives rise to the first total syntheses of calystegine B(3) and B(4).     

A short route to dehydro [12] annulenes.

A novel synthesis of dehydro [12] annutenes from 1,2-dibromobenzene is based on selective Pd(0)-Cu(1) coupling reactions of aryl and vinyl halides with tenninal acetylenes.     

Benzomorphan related compounds. II. New synthesis route to thienomorphans

A new synthesis route to α-2,5,9-trimethylthieno[3,2-f]morphan and two analogous compounds from cyanopyridines and 2-thienyllithium is described. Spectroscopic data of these substances and their intermediates are included.