Longest Linear Sequence Research Articles

Total synthesis of the latrunculins

The total syntheses of (+)-latrunculin A (1) and (+)-latrunculin B (2), two architecturally novel toxins isolated from the Red Sea sponge Latrunculia magnifica (Keller), have been achieved via highly convergent and stereocontrolled routes (longest linear sequences, 16 and 12 steps, respectively). Formal syntheses of scalemic latrunculins C (3) and M (5) also derive from the construction of 2. Central features of the unified synthetic strategy include the aldol reaction of aldehyde (-)-12 with methyl ketone (-)-13, a novel acid-catalyzed reorganization-equilibration of ortho ester (-)-11, and Mitsunobu macrolide cyclization

The chemistry of cyclic vinyl ethers. 6. Total synthesis of polyether ionophore antibiotics of the calcimycin (A-23187) class

An extremely convergent (longest linear sequence, 16 steps), fully stereoselective, and potentially general synthesis of the antibiotic ionophores of the Calcimycin (A-23187) class was devised. The key steps involve a coupling reaction between the chiral nonracemic subunits dihydropyran 41 (as the α-lithio anion) and bromide 49. Subsequent acid-promoted cyclization directly produces the spirocyclic ring system found in the ionophore X-14885A (3). Alternatively, cyclopropanation of substituted vinyl ether 55 followed by acid treatment afforded the spiroketal 58 that was subsequently converted into the polyether ionophore Calcimycin (1) and also Cezomycin (2)

ChemInform Abstract: A Concise Asymmetric Synthesis of the Seco Acid of Erythronolide B.

The concise synthesis of 3,a protected derivative of the seco acid of erythronolide B, has been achieved by a convergent approach wherein the longest linear sequence employs only 14 chemical operations with the total number of steps being 18. The approach is efficient, and substantial quantities of material may be prepared

A new synthesis of defucogilvocarcin M

A convergent synthesis of the title compound is described. The synthesis revolves around a MAD-mediated coupling of oxazoline 11 and naphthoquinone ketal 16 and requires eight steps via the longest linear sequence.