Neighboring group participation in Lewis acid-promoted [3 + 4] and [3 + 5] annulations. The synthesis of oxabicyclo[3.n.1]alkan-3-ones
作者:Gary A. Molander、Kimberly O. Cameron
DOI:10.1021/ja00056a002
日期:1993.2
2-(alkoxycarbon)-m-oxabicyclo[3.n.1]alkan-3-ones can be constructed by this process in which two new carbon-carbon bonds are generated. Unusually high regioncontrol is observed, and good to excellent stereochemicalcontrol can be achieved at virtually every position on the new carbocycles. Intramolecular neighboringgroupparticipation is proposed to explain the unusually high selectivities attained in the annulation
Total Synthesis of the Tiacumicin B (Lipiarmycin A3/Fidaxomicin) Aglycone
作者:Florian Glaus、Karl-Heinz Altmann
DOI:10.1002/anie.201409510
日期:2015.2.2
tiacumicinB, we have developed an efficient approach to the synthesis of the tiacumicinB aglycone. The synthesis features a high‐yielding intramolecular Suzuki cross‐coupling reaction to effect macrocyclic ring closure. Key steps in the synthesis of the macrocyclization precursor were a highly selective, one‐pot Corey–Peterson olefination and an ene–diene cross‐metathesis reaction. Depending on the
Synthesis of the atropurpuran A-ring via an organocatalytic asymmetric intramolecular Michael addition
作者:Huan Chen、Dan Zhang、Fei Xue、Yong Qin
DOI:10.1016/j.tet.2013.02.078
日期:2013.4
The asymmetric synthesis of the A-ring fragment 2a–b of atropurpuran 1 has been achieved in 15 steps with up to 70% ee via an organocatalytic intramolecularMichaeladdition of nitroalkene 10. The absolute configuration of the two contiguous carbon centers in 2a and 2b was assigned to be (4S, 5R) and (4R, 5R), respectively, using the modified Mosher's method.
Action des dialkylcuprates de lithium sur les aldéhydes α,β -éthylénioues
作者:C. Chuit、J.P. Foulon、J.F. Normant
DOI:10.1016/0040-4020(80)80126-8
日期:1980.1
Nearly exclusive 1-4 addition produts obtained by action of lithium dialkylcuprates with α,β ethylenic aldehydes. Non polar solvents and low temperatures favour this reaction .Only α,β-ehylenic aldehydes having a trisubstituted double bond give a relatively important proportation of 1–2 addition product.
Various branched alkylcarbenes have been generated by alkaline decomposition of the corresponding tosylhydrazones. The intramolecular insertion reactions of these carbenes (formation of cyclopropanes) proceed with appreciable discrimination which depends strongly on steric effects. The product ratios are consistently explained by a transition state with approximately planar (eclipsed) configuration