A Convergent Synthetic Route to (+)-Dynemicin A and Analogs of Wide Structural Variability

Abstract

In a similar fashion, bis(triphenylphosphine)palladium(II) chloride (3.64 g, 5.17 mmol, 0.050 equiv) was added (at 0 oC) and the resulting mixture was deoxygenated once again at-78 oC. The deoxygenated reaction suspension was then warmed to 23 oC and was stirred at that temperature for 3 h. The brown product solution was washed with a 1:1 mixture of saturated aqueous potassium carbonate solution and saturated aqueous ammonium chloride solution (3 x 150 mL). The organic layer was dried over sodium sulfate and was concentrated. The residue was purified by distillation under reduced pressure (bp 45-50 oC, 0.5 mm Hg) to afford (Z)-1-chloro-4-(tertbutyldimethylsilyl)-1-buten-3-yne (32) as a colorless oil (12.5 g, 60%

Enzymatically Asymmetrised Chiral Building Blocks for the Synthesis of Complex Natural Product Analogues: The Synthesis of Dynemicin Analogues from 2‐(Quinolin‐4‐yl)propane‐1,3‐diol

“…Moreover, the sign of optical rotation of 74a (+394.2) is the same as that of natural dynemicin and also of the simplified dynemicin analogues with the same absolute configuration. [23,24,72] The preparation of 74a represents the first asymmetric synthesis of a simplified dynemicin analogue. It is worth noting that, to the best of our knowledge, enantiomerically pure simplified analogues 1 had been prepared in only two cases.…”

Application of the Tf2O/2-chloropyridine couple in the synthesis of novel 4,5-unsubstituted N-carbamoyl-2,3-dihydroisoxazoles

“…Fortunately, 2-chloropyridine has been successfully used along with Tf 2 O in several examples as a considerably cheaper and a satisfactory alternative to the above-mentioned bases. 15,16 It is worth noting that its application often activates nonreactive substrates and significantly improves the yields when used instead of other hindered pyridine bases. We have also found 2-chloropyridine to be beneficial for the presented eliminations.…”

Direct Observation of Intermediates Involved in the Interruption of the Bischler–Napieralski Reaction

“…1 These transformations often include condensation reactions that are sensitive to the base additive or presence of Lewis basic functional group. We have found the Tf 2 O–2-chloropyridine reagent combination, first reported by Myers for the synthesis of a key vinyl trifluoromethanesulfonate in their total synthesis of (+)-dynemicin A 2 and later by Gin for dehydrative glycosylation chemistry, 3 to be particularly effective for electrophilic amide activation leading to an array of versatile condensation reactions that include syntheses of substituted pyridines, 4 pyrimidines, 5,6 alkynyl imines, 7 isoquinolines and β-carbolines. 8 We also first reported the use of the Tf 2 O–2-fluoropyridine reagent combination for direct dehydrative N -pyridinylation of amides.…”