Stereoselective total synthesis of almorexant

A highly stereoselective synthesis of almorexant has been achieved using (R)-tert-butanesulfinamide as a chiral source. The chiral tetrahydroisoquinoline core was constructed through allylation of chiral N-sulfinyl imine followed by ring closure of the secondary amide with a tethered halide. The chiral α-phenyl amide was introduced by means of S_N2 substitution of (S)-methyl 2-phenyl-2-(tosyloxy)acetate with chiral tetrahydroisoquinoline.     

Asymmetric synthesis of macrolactin analogue

Total asymmetric synthesis of macrolactin A analogue was accomplished by the convergent strategy. Rapid access to advanced intermediate 16 through isomerization of ynone to (E,E)-conjugated dienone is a key step of this synthesis. Overall, control of all of the four stereocenters was achieved by means of asymmetric and diastereoselective reactions without using any chiral natural sources.     

Facile synthesis of regio-isomeric naphthofurans and benzodifurans

Naphtho[1,2-b]furans 1a-f, naphtho[2,1-b]furans 2a-f, benzo[1,2-b:5,4-b′]difurans 3a-b, benzo[1,2-b:4,5-b′]difurans 4a-b, and benzo[1,2-b:4,3-b′]difurans 5a-b were synthesized by base-catalyzed cyclization reaction of the corresponding o-alkoxybenzoylarene derivatives. The o-alkoxybenzoylarenes were obtained from the etherification reaction of the o-hydroxybenzoylarenes, which were prepared either by the reaction of methoxyarenes with benzoyl chloride in the presence of aluminum chloride or by photo-Fries rearrangement of aryl benzoates.     

Diastereoselective synthesis of homo-N,O-nucleosides

A new class of homo-N,O-nucleosides has been designed, based on the 1,3-dipolar cycloaddition of C-substituted nitrones with allyl nucleobases. The N-methyl-C-ethoxycarbonyl nitrone 1, and the C-α-silyloxymethyl-N-methyl nitrone 7 have been exploited: the stereochemical features of the obtained nucleosides are dependent on the nature of the dipole. The results obtained with DFT calculations fully agree with the experimental results and successfully reproduce the experimentally observed reversal of endo/exo selectivity for nitrones 1 and 7.     

First total synthesis of fumaridine

The first total synthesis of the alkaloid fumaridine 1a is reported. The key step is the assemblage of the arylmethylene isoindolinone 2a (E) by Horner reaction between the phosphorylated isoindolinone 3a and the suitably substituted benzaldehyde 4. N-Lactam deprotection and concomitant E→Z isomerization complete the synthesis of the title compound.     

Pd-NHC-catalyzed synthesis of diaryl ketones

With N-hetereocyclic carbene and palladium catalysis, diaryl ketones with a variety of functional groups that span from electron withdrawing to electron donating substitutions can be conveniently synthesized using the corresponding aryl boronic acid and N-acyloxyphthalimide.     

Acetyltrimethylsilane mediated synthesis of dihydrophenanthrenes

An easy and efficient synthesis of phenanthrene derivatives through base catalyzed ring transformation of 4-sec-amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with acetyltrimethylsilane is described in good yields. The advantage of this reaction is the direct transformation of 2-oxobenzo[h]chromene into phenanthrene via C-C insertion from acetyltrimethylsilane.     

An efficient synthesis of semiplenamide C

Semiplenamides are anandamide-like fatty acid amide metabolites previously isolated from a marine cyanobacterium that display a range of biological activity. Novel syn-aldol/dehydration methodology has been developed for the stereoselective synthesis of the core (E)-α,β-unsaturated amide functionality of this class of natural product, and employed for the efficient synthesis of semiplenamide C.     

Practical and efficient synthesis of N-halo compounds

A practical and efficient synthesis of N-halo compounds is described. Treatment of primary and secondary amines or amides with sodium hypohalite in the presence of tert-butanol and acetic acid afforded N-halo compounds in 90-100% yield.     

Facile synthesis of C-phosphanylformamidines via a carbene pathway

A direct synthetic approach to C-phosphanyl-N,N-dialkyl-N′-aryl(alkyl)-formamidines was developed. It was shown that phosphorylation of the formamidines proceeds at the nitrogen atom affording N-phosphanylformamidinium salts. Upon deprotonation, these salts gave C-phosphanylformamidines via formation of carbenes followed by a 1,2-phosphorus shift.     

The first total synthesis of trichostatin D

Trichostatin D and 6-epi-trichostatin D have been stereoselectively synthesized through a remote stereoinduction with a chiral vinylketene silyl N,O-acetal and glycosylation of hydroxyimide under Mitsunobu conditions.     

Concise total synthesis of flavone C-glycoside having potent anti-inflammatory activity

The total synthesis of anti-inflammatory active flavone C-glycoside isolated from oolong tea extract is achieved. Introducing a C-glucosyl moiety to an aryl system and constructing a fused tetracyclic ring characteristic to this natural product were conducted based on the O-to-C rearrangement of sugar moiety and the successive intramolecular Mitsunobu reaction, respectively. This concise and efficient synthetic pathway is applicable to the large-scale synthesis of target flavone and for constructing a large library of related compounds.     

Solvent-free synthesis of azole carboximidamides

A one-pot procedure is described for the preparation of 1H-pyrazole-carboximidamides 2, 1H-benzotriazole-carboximidamides 3 and guanidinylation of amines with 3. The X-ray crystal structure of N,N-dimethyl-1H-benzotriazole-1-carboximidamide 3b, has been determined.     

Total synthesis and structure revision of petrobactin

The total synthesis and the revised structural assignment of petrobactin, a siderophore isolated from the marine bacterium Marinobacter hydrocarbonoclasticus, is reported. The key step in the synthesis involved condensation of N¹-(2,3-dibenzoyloxybenzoyl)-N⁴-benzylspermidine with 1,3-di-(p-nitrophenyl)-2-tert-butyl citrate. Proton NMR spectra of the synthesized product compared with those reported for the natural product revealed that the compound did not contain 2,3-dihydroxybenzoyl moieties as published; instead, the splitting pattern suggested 3,4-dihydroxybenzoyl fragments. The 3,4-dihydroxybenzoyl analogue was accessed via a similar route; the proton and carbon-13 NMR spectra of this compound were consistent with those reported for natural petrobactin.     

Efficient synthesis of arylaminotetrazoles in water

Arylaminotetrazole derivatives are synthesized efficiently by the reaction of arylcyanamides and sodium azide in the presence of ZnCl₂ under aqueous conditions at reflux. Generally, isomer of 5-arylamino-1H-tetrazole can be obtained from arylcyanamides carrying electron-withdrawing substituent on aryl ring and as the electropositivity of substituent is increased, the product is shifted toward the isomer of 1-aryl-5-amino-1H-tetrazole.     

Stereoselective synthesis of swainsonines from pyridines

An efficient synthesis of (−)-swainsonine and (−)-2,8a-di-epi-swainsonine was developed starting from readily available 2-pyridinecarbaldehyde and 3-hydroxypyridine. In particular, it was demonstrated that the mixture of simple indolizidines, i.e. lentiginosine and epi-lentiginosine, being readily available by a number of different synthetic routes, can be directly converted to swainsonine.     

An asymmetric synthesis of (+)-desoxoprosophylline

An efficient synthesis of (+)-desoxoprosophylline is described. The key steps in the reaction sequence include the preparation of an N-Cbz-sulfilimine from the corresponding sulfoxide using the Burgess reagent, regio- and stereoselective hetero-functionalization of an alkene using the pendant sulfilimine as the nucleophile and a stereoselective amidomercuration to form the cis-2,6-disubstituted piperidine ring.     

An efficient synthesis of highly substituted pyrroles from β-oxodithiocarboxylates

α-Oxoketene-N,S-acetals, prepared by the reaction of alkyl glycinate hydrochlorides with β-oxodithiocarboxylates followed by alkylation, underwent cyclization in presence of chloromethyleneiminium salt derived from POCl₃/DMF to afford alkyl-3-aryl-4-formyl-5-(alkylsulfanyl)-1H-pyrrole-2-carboxylates in excellent yields. Alkyl-3-aryl-5-(alkylsulfanyl)-1H-pyrrole-2-carboxylates were formed in moderate yields when the same N,S-acetals were treated with DBU.     

A polystyrene-supported triflating reagent for the synthesis of aryl triflates

An insoluble polystyrene-supported triflating reagent has been prepared by suspension co-polymerization of N-(4-vinylphenyl)trifluoromethanesulphonimide, styrene and the JandaJel^® cross-linker. This reagent, in the presence of triethylamine, allows for the efficient synthesis of aryl triflates from a wide range of phenols in a process that permits the desired product to be isolated from the reaction mixture in essentially pure form via several filtration and concentration operations. Adding to the utility of this reagent is its ability to be easily recovered, regenerated and reused. Both soluble and insoluble bifunctional polymers containing trialkylamine moieties in addition to triflimide groups were also prepared and examined as triflating reagents. Unfortunately these reagents afforded only modest yields of the desired products in representative reactions.     

Total synthesis of malayamycin A and analogues

The total synthesis of the bicyclic C-nucleoside malayamycin A is described starting with d-ribonolactone. A new method was developed to obtain preparatively important quantities of β-pseudouridine, which was used as an intermediate. The synthesis of a carba N-nucleoside analogue of malayamycin A is also described.