A strategy was developed for the first total synthesis of clonostachydiol which inturn would assign the absolute configuration, based on the chiron approach, using carbohydrate derived chiral synthons. This study however culminated in the synthesis of (2R,3R,8R,11S) isomer of clonostachydiol.
Water-soluble hydroxocomplexes 2, easily formed from organotin trihalides 1 in aqueous alkaline solution, react readily with aryl halides in the same medium in the presence of palladium complexes to give cross-coupled products 3 in high yields.
Thieno[2,3(3,2)-f] indolizines were synthesized from 2-formyl-1-[thien-2(3)-ylmethyl]pymole. Under Diels-Alder reaction with diethyl acetylenedicarboxylate they led to cycl[3,2,2]azines fused to a thiophene ring.
The sex pheromone of the brownbanded cockroach, Supella longipalpa, can be synthesized by direct coupling of a brominated pyrone with an alkylzinc reagent. The stereochemistry of the natural pheromone has been assigned as (2′R, 4′R)-5-(2′,4′-dimethylheptanyl)-3-methyl-2H-pyran-2-one by a combination of synthesis, chiral gas chromatography, and electrophysiological measurement.
Nucleophilic substitution reactions of 4-azolyl-1-β-D-ribofuranosylpyrimidin-2(1H)-one and 6-azolyl-9-β-D-ribofuranosyl-9H-purine derivatives, which were converted from uridine and inosine, with [ 15 N]phthalimide in the presence of triethylamine or DBU were found to give [4- 15 N]-N 4 -phthaloylcytidine and [6- 15 N]-N 6 -phthaloyladenosine derivatives, respectively,...
Treatment of the acyl selenide 7 with triphenyltin hydride and triethylborane generates the acyl radical which undergoes 5-exo trigonal cyclization to afford the 2,5-disubstituted tetrahydrofuran-3-ones 10a/b in 97% yield as a 94:6 mixture of diastereoisomers.
Conjugate addition-rearrangement of N-benzylhydroxy-lamine to lactone 6 provides isoxazolidin-5-one 7 which was in turn mesylated at the hydroxy group and subjected to the next skeleton rearrangement to afford 3,5-disubstituted isoxazolidine 10. Standard transformation of 10 gave negamycin lactone 4.
α-Ketosulphides of benzothiazole 1 react with allylic carbonates in the presence of palladium acetate in dichloromethane under mild conditions affording α,α-diallylated ketosulphides 2 in high yields. Reduction of 2 with sodium borohydride in isopropanol gives episulphides which in turn can be transformed almost quantitatively into trienes.
Dialdehydes derived from digoxin glycosides via sodium periodate oxidation were regioselectively deglycosylated by various amino acids in anhydrous methanolic solution to afford excellent yields of digoxigenin bis-digitoxoside and digoxigenin mono-digitoxoside in a single step.
The title reactions are shown to proceed with sterically unfavorable syn preference (to the siloxy group) when steric demand of the acetals is trivial, whereas β-substitution of acetals results in reversal of diastereoselection. These results are discussed in terms of the stereoelectronic vs. steric effect.
New chiral nitroenamines 4a,b were found to be very effective for asymmetric nitroolefination of α-alkyl-γ- and δ-lactones. The enantiomeric excess of the product ran up to 99 %. A possible chelation model for the transition state of the asymmetric nitroolefination was discussed.
The reaction of phenethyliminophosphorane with arylketenes gave 1-benzyl-3,4-dihydroisoquinolines in good yields. An aza-Wittig type reaction of vinyliminophosphorane with p-toluenesulfonylisocyanate furnished 1-aminoisoquinoline 6 in high yield.
8,10-Dimethoxyellipticine has been synthesised from readily available benzene derivatives via palladium acetate or photochemical cyclisation of intermediate diphenylamine derivatives. The route has advantages over indole based syntheses.
Chiral, non-racemic sulfoxides were reacted with thiols and BSA in the presence of a catalytic amount of TMSOTf in MeCN at rt overnight to give the corresponding chiral, non-racemic anti-thioacetals with high diastereoselectivity.
3,6,9,12,15,18-Hexaphenyl-1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydroannulene and related compounds have been synthesized. These compounds were found to be stable both in crystalline forms and chloroform solution at room temperature, to have aromatic character by the existance of a diamagnetic ring current on the basis of the nmr spectral data, and to conform to the D 6h -symmetry group.
Reaction of benz[a]azulene with dimethyl acetylenedicarboxylate (DMAD) in tetralin at 200 °C gave a new π-electron system, dimethyl benzo[a]heptalene-6,7-dicarboxylate and dimethyl indenol[1,2,3-cd]azulene-5,6-dicarboxylate. The reaction of a non-fused azulene, 6-isopropyl-1-phenylazulene, gave extremely different results indicating strong effects of the fused benzene ring on the reactivities of azulenes...
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