Kinetically controlled total syntheses of dl-trachelanthamidine and dl-isoretronecanol

Ring Opening of Donor–Acceptor Cyclopropanes with N-Nucleo­philes

“…97 The devised method was employed in racemic syntheses of pyrrolizidine alkaloids (±)-isoretronecanol and (±)-trachelanthamidine (Scheme 37). 98 Danishefsky suggested an analogous approach in the synthesis of pyrroloindoles 86 and 89, which can be viewed as structural analogues of mitomycin С (Scheme 38). …”

“…The strategy of forming bicyclic γ-lactams, derivatives of pyrrolizinone and indolizinone, was described in the works of Danishefsky et al [97][98][99] It was based on the intra- …”

Propynyllithium

“…3-Tetrahydropyranyloxy-1-propyne, after lithiation in THF with n-BuLi, selectively displaces the bromide of 1-chloro-3bromopropane after 20 h at 70 • C. 17 or couples with one end of 1,3-dibromopropane in the presence of Hexamethylphosphoric Triamide. 18 The sluggishness of these alkylations has been overcome by the use of triflate as the leaving group and a mixed solvent system of THF-N,N -Dimethylpropyleneurea (6:1). Under these conditions, the TBS ether of propargyl alcohol, after lithiation, displaces the primary triflate, which is a particularly difficult substrate due to the β-oxygen functionality, in 10 min at −20 • C (eq 12).…”

Stereospecific total synthesis of dl-hastanecine and dl-dihydroxyheliotridane

“…cyano-1 -methylethyl)triptycene.3 Previously, we reported the synthesis of 9,9'-bitriptycyl. 4 We report herein on 2,2'-dimethyl-9,9'-bitriptycyl (1), which exhibits an enormous rotational barrier between the central 9 and 9' sp3-hybridized carbon atoms, in excess of 54 kcal mol-1. The synthesis of 1 is outlined in Scheme I.…”

“…The synthesis of 1 is outlined in Scheme I. 5 The NMR spectrum, in CDCI3, of the initially isolated material from column chromatography exhibited two closely spaced singlets at 1.83 and 1.81 (ArCPU). In repetitive experiments, the higher field singlet was ~50-80% the height of the lower field singlet.…”