Convenient method of synthesizing 3-ethoxycarbonyl indoles

We have developed a convenient two-step procedure for the synthesis of 3-ethoxycarbonyl indoles from commercially available materials. The two-step procedure involves the synthesis of 2-aryl-3-hydroxypropenoic acid ester, followed by a catalytic reduction. This method is efficient, simple, and selective.     

A new and versatile synthesis of 3-substituted oxetan-3-yl methyl alcohols

We have developed a novel route for the efficient synthesis of pharmaceutically significant 3-substituted oxetan-3-yl methyl alcohols starting from readily available malonates. The synthesis harnesses the diversity of malonate chemistry and allows access to a range of oxetanes, which exemplifies the versatility of this procedure.     

Total synthesis of the tricyclic marine alkaloids (-)-lepadiformine, (+)-cylindricine c, and (-)-fasicularin via a common intermediate formed by formic acid-induced intramolecular conjugate azaspirocyclization

A very short and efficient enantioselective total synthesis of the tricyclic marine alkaloids (-)-lepadiformine (3), (+)-cylindricine C (1c), and (-)-fasicularin (4) has been developed utilizing the formyloxy 1-azaspiro[4.5]decane 5 as a common intermediate. The key strategic element for the synthesis was the formic acid-induced intramolecular conjugate azaspirocyclization, which proved to be a highly efficient and stereoselective way to rapid construction of the 1-azaspirocyclic substructure of these natural products in a single operation. Thus, the common intermediate 5, synthesized in two steps with 70% overall yield starting from the known (S)-N-Boc-2-pyrrolidinone 7 via the conjugate spirocyclization using an acyclic ketoamide 6, was utilized for the concise and stereoselective total synthesis of (-)-lepadiformine (3), which was accomplished in seven steps with 45% overall yield from 5 (31% yield from 7). The developed strategy based on the conjugate spirocyclization was also applied to the stereoselective total synthesis of (+)-cylindricine C (1c), which was achieved in 10 steps from 5 in 18% overall yield (12% yield from 7). Further application of this approach using 5 led to the synthesis of (-)-fasicularin (4), wherein an extremely efficient method for the introduction of the thiocyanato group via an aziridinium intermediate at the last step was developed. Thus, the highly efficient first enantioselective total synthesis of (-)-fasicularin was accomplished in nine steps with an overall yield of 41% from 5 (28% yield from 7).     

One-pot synthesis of 1-monosubstituted-1, 2, 3-triazoles from 2-methyl-3-butyn-2-ol

An efficient method for the synthesis of 1-monosubstituted-1, 2, 3-triazoles from 2-methyl-3-butyn-2-ol under copper catalyst conditions has been developed through a one-step one-pot sequence. This method provides a concise and efficient pathway to synthesize 1-monosubstituted-1, 2, 3-triazole derivatives in good to excellent yields.     

A new, more efficient, and effective process for the synthesis of a key pentacyclic intermediate for production of ecteinascidin and phthalascidin antitumor agents

An efficient process is described for the synthesis of 5, a key intermediate for the synthesis of the potent antitumor agents ecteinascidin 743 (1) and phthalascidin (2) from the readily available building blocks 3b and 4.     

Dienamines as diels-alder dienes. An efficient synthesis of a key intermediate for drimane-related sesquiterpenes

An efficient synthesis of dienediester 3, a key intermediate for drimane-related sesquiterpenes, is described starting from enal 4.     

PPh3⋅HBr‐DMSO Mediated Expedient Synthesis of γ‐Substituted β,γ‐Unsaturated α‐Ketomethylthioesters and α‐Bromo Enals: Application to the Synthesis of 2‐Methylsulfanyl‐3(2 H)‐furanones

An efficient chemoselective general procedure for the synthesis of γ‐substituted β,γ‐unsaturated α‐ketomethylthioesters from α,β‐unsaturated ketones has been achieved through an unprecedented PPh₃?HBr‐DMSO mediated oxidative bromination and Kornblum oxidation sequence. The newly developed reagent system serves admirably for the synthesis of α‐bromoenals from enals. Furthermore, AuCl₃‐catalyzed efficient access to 3(2H)‐furanones from the above intermediates under extremely mild conditions are described.     

Studies on isoxazole and pyrazole formation by the reaction of trifluoromethyl-substituted anilines with oxime and hydrazone dianions

5-(2-Aminophenyl)isoxazoles are obtained in good yields by the reaction of 2-(trifluoromethyl)aniline with dilithio derivatives of oximes of acetone, 3-pentanone, propiophenone, and cyclohexanone. An analogous synthesis of a substituted isoxazole from 4-(trifluoromethyl)aniline and 3-pentanone oxime and the synthesis of a substituted pyrazole from 2-(trifluoromethyl)aniline and 3-pentanone hydrazone are less efficient.     

A Three-Step Preparation of 3-Isopropylcatechol

An efficient synthesis of 3-isopropylcatechol from veratrole is described.     

A practical route to enantiopure 3-hydroxy-pyrrolidines: application to a straightforward synthesis of (−)-bulgecinine

A practical synthesis of enantiopure substituted 3-hydroxy-pyrrolidines is reported. In four steps, starting from commercially available amino acids as chiral educts, this method allows for an efficient preparation of a variety of 3-hydroxy-pyrrolidines, as well as 3-hydroxy-piperidines and azepanes. Application of this methodology for a straightforward asymmetric synthesis of (−)-bulgecinine is also described.     

Efficient one-pot synthesis of n-butyl levulinate from carbohydrates catalyzed by Fe_2(SO_4)_3

Butyl levulinate(BL) is a promising new candidate as diesel fuel and fuel additive. In this study, an efficient process for a one-pot synthesis of BL from biomass-derived carbohydrates in butanol medium with the catalysis of metal sulfates was developed. The catalytic activity of a series of metal sulfates for the synthesis of BL from fructose was investigated. Among various metal sulfates, ferric sulfate Fe_2(SO_4)_3 was found to be the most efficient catalyst, which gave a remarkably high BL yield of 62.8 mol% under the conditions of 463 K, 3 h, a catalyst dosage of 5.0 g/L, and fructose concentration of 25 g/L. Different carbohydrates including glucose, cellulose, inulin and sucrose were also used for one-pot synthesis of BL with the catalysis of Fe_2(SO_4)_3, showing the yields of 39.6, 30.5, 56.6 and 50.1 mol%, respectively. In addition,the recycling and reuse of Fe_2(SO_4)_3 was studied by characterizing them using powder X-ray diffraction(XRD), scanning electron microscope(SEM), X-ray photoelectron spectroscopy(XPS). A plausible reaction pathway for the one-pot synthesis of BL from fructose was proposed. This study provides a facile and feasible way for the synthesis of BL from biomass.     

Regioselective synthesis of 2-(2-hydroxyaryl)pyridines from the reactions of benzynes with pyridine N-oxides

By modifying the conditions from those in Larock's reported synthesis of 3-(2-hydroxyaryl)pyridines from benzynes, and pyridine N-oxides, we altered the regioselectivity of the reaction toward an efficient synthesis of 2-substituted pyridines. The presence of ethyl propiolate altered the regioselectivity to afford 3-substituted pyridine products instead. We conducted appropriate control experiments that enable a full understanding of the mechanism.     

An efficient route to pyrimidine nucleoside analogues by [4 + 2] cycloaddition reaction

We report here an efficient synthesis for pyrimidine nucleoside analogues by [4 + 2] cycloaddition reaction. These compounds were obtained by convergent chemistry from glycosyl isothiocyanates 3a-f (pyranoses, furanoses, and dissaccharides) and diazadienium salt 5. In fact, diazapentadienium iodide 5 prepared from vinylthioamide 4 is an efficient intermediate in heterocyclic synthesis and reacts with isothiocyanates 3a-f affording beta-D-uracil analogues 7a-f in good yields and with total regiocontrol. All compounds were fully characterized by IR, HRMS, and 13C and 1H NMR (COSY and HMQC).     

Synthesis of polyhydroxycyclohexanes and relatives from (-)-quinic acid

An efficient and versatile strategy for the synthesis of polyhydroxycyclohexanes and related compounds 3-6 is reported. The successful synthesis of these analogues has been achieved from a common intermediate, quinic acid derived lactone 2, rapidly accessible from cheap and commercially available (-)-quinic acid (1) as a chiral template. A practical route involving stereocontrolled epoxide formation and hydrolysis has been developed for the synthesis of 2,3-trans analogues 3 and 4. The preparation of the 2,3-cis analogues 5 and 6 has been realized by diasteroselective oxidation of a 5,6-double bond.     

A new short synthesis of 3-substituted 5-amino-1-(chloromethyl)-1,2-dihydro-3H-benzo[e]indoles (amino-CBIs)

A new short synthesis of 3-substituted 5-amino-1-(chloromethyl)-1,2-dihydro-3H-benzo[e]indoles from Martius Yellow is disclosed. The key steps of the synthesis were three efficient regioselective reactions (iodination, 5-exo-trig aryl radical-alkene cyclization and carboxylation).     

NHC‐Catalyzed Asymmetric Synthesis of Functionalized Succinimides from Enals and α‐Ketoamides

The efficient asymmetric synthesis of highly substituted succinimides from α,β‐unsaturated aldehydes and α‐ketoamides via NHC‐catalyzed [3+2] cycloaddition has been developed. The new scalable protocol significantly expands the utility of NHC catalysis for the synthesis of heterocycles and provides easy access to assemble a wide range of succinimides from simple starting materials.     

Synthesis of heterosteroids. First synthesis of oxa steroid from cholic acid

We wish to report here a new and efficient partial synthesis of 3-oxa-5β-steroid, the first oxa steroid synthesized from cholic acid.     

Parallel synthesis of a vitamin D(3) library in the solid-phase.

A highly efficient synthesis of the vitamin D(3) system on solid support is described. Two synthetic strategies for the solid-phase synthesis of vitamin D(3) were developed. One is for 11-hydroxy analogues, and the other is for most other synthetic analogues. In the latter strategy, the sulfonate-linked CD-ring 58 was initially immobilized on PS-DES resin to give solid-supported CD-ring 63 (Scheme 10). Similarly, solid-supported CD-ring 63 was prepared by attachment of the CD-ring 10 to the chlorosulfonate resin 64. The vitamin D(3) system was synthesized by Horner-Wadsworth-Emmons reaction of the A-ring phosphine oxide to a solid-supported CD-ring, followed by simultaneous introduction of the side chain and cleavage from resin with a Cu(I)-catalyzed Grignard reagent. Parallel synthesis of the vitamin D(3) analogues was accomplished by a split and pool methodology utilizing radio frequency encoded combinatorial chemistry, and a manual parallel synthesizer for side chain diversification and deprotection. Additionally, we demonstrated the synthesis of various A-rings in a similar protocol for efficient preparation of building blocks.     

An efficient one-pot synthesis of 3-substituted-5-amino-1,2,4-thiadiazoles from isothiocyanates and amidines

An efficient one-pot synthesis of 3-substituted-5-amino-1,2,4-thiadiazoles from isothiocyanates and amidines is described.     

An improved synthesis of 3-aminoestrone

An efficient Pd(0)-catalyzed protocol for the rapid and efficient preparation of 3-aminoestrone via 3-benzylaminoestrone from estrone-triflate is described. The three step synthesis proceeds with an overall yield of about 55% using X-Phos as optimal ligand for the Pd(0)-catalyzed Buchwald-Hartwig amination.