Synthetic study of gymnocin-A: synthesis of the ABC ring fragment

Homologation Reaction of Ketones with Diazo Compounds

“…The ring expansion protocol using TMSCHN 2 was also applied to the linear total synthesis of hemibrevetoxin B natural product (Scheme ). Such a strategy was first used in the expansion of tricyclic ketone 164 and later in the expansion of tetracyclic ketone 166 to provide the seven-membered rings. − The method was later employed in the synthesis of gambierol for the ring expansion to the seven-membered ether E ring, − in the construction of the BC and KLMN ring systems of 168 and 169 , respectively, toward total synthesis of gymnocin-A and on the oxepane core in a enantiodivergent synthesis of (+)- and (−)-isolaurepan. , A divergent synthesis of trans -fused octacyclic polyether 170 and derivatives was recently achieved by introducing the ring-expansion procedure at suitable stages. The reaction was applied to the expansion of six- and seven-membered ether rings at several stages along the synthetic path, with preferential migration of the less-substituted carbon .…”

“…Such a strategy was first used in the expansion of tricyclic ketone 164 and later in the expansion of tetracyclic ketone 166 to provide the seven-membered rings. 285−287 The method was later employed in the synthesis of gambierol for the ring expansion to the seven-membered ether E ring, 288−292 in the construction of the BC 293 and KLMN 294 ring systems of 168 and 169, respectively, toward total synthesis of gymnocin-A and on the oxepane core in a enantiodivergent synthesis of (+)-and (−)-isolaurepan. 295,296 A divergent synthesis of trans-fused octacyclic polyether 170 and derivatives was recently achieved by introducing the ringexpansion procedure at suitable stages.…”

Development of New Synthetic Methods Using Oxiranyl Anions and Application in the Syntheses of Polycyclic Ether Marine Natural Products

“…Synthesis of ABC Fragment 140 system among known polycyclic ethers after brevisulcenal-F 75) and gymnocin-B. 76,77) The total synthesis of gymnocin-A has only been achieved by Tsukano and Sasaki [78][79][80] using an [X + 1 + Y] approach 8) via the B-alkyl Suzuki-Miyaura cross coupling. Our successful total synthesis of gymnocin-A highlights the efficient assembly of polyether units by the iterative use of the [X + 2 + Y] convergent method based on the oxiranyl anion strategy.…”

Synthesis of the GHIJKL Fragment of Gymnocin-B

“…Meanwhile, the ring system of the remaining part (D–O) of gymnocin-B is completely different from that of gymnocin-A. Several synthetic studies have been reported thus far for gymnocin-A, and total synthesis of gymnocin-A has been accomplished by two groups including ours . Synthesis of gymnocin-B is more challenging due to its longer and more complex structure.…”