A Structural Model for the Galactose Oxidase Active Site which Shows Counteranion-Dependent Phenoxyl Radical Formation by Disproportionation

✍ Scribed by Yuichi Shimazaki; Stefan Huth; Akira Odani; Osamu Yamauchi

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 124 KB
• Volume: 112
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/(sici)1521-3757(20000502)112:9<1732::aid-ange1732>3.0.co;2-x

✦ Synopsis

Galactose oxidase (GO) contains one copper ion at its active site and performs a two-electron oxidation of primary alcohols to aldehydes, coupled with a reduction of O 2 to eomer in 68 % yield. The entire sequence was performed in 24 linear steps from (S)-malic acid. The material thus obtained was shown to be identical in all respects to natural griseoviridin [20] ( 1 H, 13 C NMR, [a] D , etc.).

The sequence leading to C-8 epi-griseoviridin [21] was performed in exactly the same manner and led to a product, in comparable yields, that was distinctly different from natural griseoviridin in its spectroscopic properties. Attempts to ascertain whether ene ± thiol lactone 5 could be interconverted to its C-8 epimer proved fruitless due to decomposition when strong bases were employed. Further, attempts to incorporate deuterium into the C-8 position of 5 also failed. In summary, griseoviridin and its C-8 epimer have been synthesized for the first time employing a novel ring-closing metathesis which involved a highly diasteroselective triene to diene macrocyclic ring formation.