Early studies on the biosynthesis of Sarubicin A, 1, had suggested the
intermediacy of the novel aromatic amino acid 6-hydroxyanthranilic acid,
17. To investigate the biosynthetic steps beyond 17, [¹³C-¹⁵N carboxamide]
6-hydroxyanthranilamide, 27a, was synthesized, and fed to fermentations
of Streptomyces helicus. Incorporation of 27a into 1 provided suggestive
evidence...
Bromoalkoxylation of dihydropyran with bromine and 1-borneol, followed by dehydrobromination and epoxidation, afforded trans-2-1- bornyloxy-3,4-epoxytetrahydropyran as a major product. This was treated with sodium phenylselenide to give a 1:1 mixture of (2R,3R,4R)- 2-1-bornyloxy-3-hydroxy-4-phenylselenotetrahydropyran and its (2S,3S, 4S) diastereomer. Elimination of the selenoxide, derived from oxidation of the former with hydrogen...