Studies of archaemycin biosynthesis

Sparkes, Andrew Windsor (1993) Studies of archaemycin biosynthesis. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The biosynthesis of archaemycin S541 factor A in a culture of Streptomyces thermoarchaencis (RS1), has been studied using ¹³C, ¹⁴C, ¹⁸O, ²H and ³H labeled precursors. The ¹³C NMR spectrum of S541 factor-A has been assigned.

Incorporation of [1-¹³C]acetate resulted in a major enrichment of carbons 1, 5, 9, 15, 17, 19 and 21, and a minor enrichment of carbons 3, 7, 11, 13, 23 and 25. With [1-¹³C]propionate, enrichment of carbons 3, 7, 11, 13, 23, and 25 was observed. Feeding [3-¹³C]propionate, produced enrichment of carbons 4a, 8a, 12a, 14a, 24a and 26a respectively. This established that the carbon skeleton of S541 factor-A, is derived from a head to tail condensation of seven acetate and six propionate units. Studies elsewhere using ¹⁸O-labeled precursors and ¹⁸O₂, have shown that out of a total of eight oxygen atoms, four are derived from acetate, three from propionate, and one from molecular oxygen. The synthesis and feeding of [3-¹³C,3-²H₃]priopionate resulted in the incorporation of [¹³C²H₃]methyl groups at carbons 4a, 12a, 14a, 24a, and 26a, and a [¹³C²H₂]methylene group at C-8a. This indicated that during the formation of the archaemycin furan ring, modification resulting in an aldehyde group at the C-8a position, is unlikely to occur. Feeding 2,2-[¹³C²H₃]isobutyrate led to intact [¹³C²H₃]methyl groups at C-29 and C-30. Efficient incorporation of [3-¹⁴C]propionate (8.45% specific incorporation per site, six sites) has been obtained. Synthesis of sodium [3-³H₁]propionate from 3-trityloxy-1-p-toluenesulphonate, afforded a white powder with a specific activity of 1.03 Ci mmole^-1. Feeding [3-³H₁]propionate yielded S541 factor-A with a specific activity of 0.38 Ci mmole^-1. Synthesis of sodium (3S)-[3-¹H₁,²H₁,³H₁]propionate from (1S)-[1-¹H₁,²H₁]-3-trityloxy-1-p-toluenesulphonate (98 % ee), afforded a white powder with a specific activity of 2.52 Ci mmole^-1.