Masahiro Hirama

EXPEDITIOUS TANDEM-METATHESIS ROUTE TO THE AB-RING FRAGMENT OF CIGUATOXIN

Abstract The AB-ring fragment of ciguatoxin was synthesized in ten steps from tri-O-benzyl- d -glucal based on a highly diastereoselective ring-closing metathesis and subsequent cross metathesis.

Synthetic study of ciguatoxin. Absolute configuration of the C2 hydroxy group

The absolute stereochemistry of the secondary alcohol of the 1,2-dihydroxybutenyl substituent of ciguatoxin (1) was shown to be S by comparing the split CD curve of ciguatoxin tetra-p-bromobenzoate (2) with those of di- and tri-p-bromobenzoates of AB ring fragments that were synthesized enantioselectively.

Enantioselective synthesis of the medium ring ethers, tetrahydrooxepin, oxocane and hexahydrooxonin, of ciguatoxin. Extensive ring-expansion and chemoenzymatic desymmetrization strategy

Abstract The extensive ring-expansion strategy for the synthesis of tetrahedrooxepin, oxocane, and hexahydrooxonin, which correspond to the D(E), I and F rings of ciguatoxin (CTX1B, 1), respectively, has been established. Chemoenzymatic acylation of the meso alcohols using a lipase provides an expeditious entry for the enantiomeric building blocks.

A very short route to the functionalized A-ring moiety of ciguatoxin

Abstract The functionalized AB-ring moiety of ciguatoxin has been synthesized in a highly convergent manner via transition metal catalysis.

The absolute configuration and total synthesis of korormicin

The marine antibiotic korormicin, isolated from the culture filtrate of marine bacterial strain Pseudoalteromonas sp. F-420, specifically inhibits the growth of marine Gram-negative bacteria without affecting terrestrial species. The absolute configuration of korormicin was determined by the combination of a CD exciton chirality method and chemical degradation. Convergent total synthesis of koromicin has been also achieved.

Practical entry into the HIJKLM ring segment of ciguatoxin CTX3C

The HIJKLM ring segment (27) of the right half portion of nciguatoxin CTX3C (1) has been synthesized using a ring-closing reaction nmediated by a low-valent titanium reagent.

Convergent synthesis of the trans-fused 6-n-6-6 (n = 7–10) tetracyclic ether system based on a ring-closing metathesis reaction

A convergent synthesis of the trans-fused 6-n-6-6 (n = 7–10) tetracyclic ether system was achieved via stereoselective alkylation and ring-closing metathesis reaction.

Convergent synthesis of the ABCDE ring framework of ciguatoxin

An alkylation–metathesis sequence is shown to be a powerful method to synthesize the ABCDE ring framework of ciguatoxin 1.

CONVERGENT SYNTHESIS OF THE IJKLM RING FRAGMENT OF CIGUATOXIN CTX3C

The IJKLM ring fragment of CTX3C, an important member of the ciguatoxin family, was synthesized via ring-closing metathesis using the Tebbe reagent and an improved method of reductive hydroxy ketone cyclization.