Synthesis of symmetric HIJ-ring model of ciguatoxin

Total Synthesis of Pestalotioprolide G and Putative Structure of Pestalotioprolide H

“…The synthesis of common acid intermediates ( rac - 12 ) of pestalotioprolides G ( 6 ) and H ( 7 ) is described in Scheme . We started our synthesis from the known mixture of intermediates rac - 17 , which were subjected to hydroindation in the presence of InCl 3 /DIBAL-H/Et 3 B followed by treatment with I 2 to result in cis -vinyl iodides rac - 18 in good yield. The TBDPS ethers of compounds rac - 18 were then deprotected by TBAF to obtain the corresponding alcohols, which were treated further with PivCl/Et 3 N followed by (TES)­OTf/2,6-lutidine to obtain compounds rac - 19 in 41% overall yield.…”

Eight-Membered Rings With One Oxygen Atom

“…121,125,126 This protocol was also extended to the synthesis of (−)-trans-lauthisan 95 126 and to the eight-membered core of the natural derivative (+)-laurencin 103. 121 Other cobalt complexes 270 and 272 were involved in the construction of the eight-membered I-ring in the synthesis of HIJfragment 189 and HIJKLM-fragment 190 of natural CTX-1B 9. Thus, the cyclization of acetylene cobalt complexes 269 and 271 occurs via intramolecular 1,4-hydroxy addition carried out in the presence of BF 3• OEt 2 in dichloromethane (Scheme 45).…”

Ciguatoxin: developing the methodology for total synthesis

“…Incidentally, a model compound with a HIJ-ring system lacking the functional group at C34, which is not depicted here, underwent the same conjugate addition to afford a single syn-trans product under basic conditions. 100 Ketone 233 was regioselectively (C39/C40) converted into the corresponding vinyl triflate, which was methylated with MeMgBr under iron catalysis. Employing an Ir catalyst, the endo-olefin 234 was hydrogenated to a single isomer 235 in 89% yield exclusively from the favored b-face.…”