Figure 6.

SDR oxidation from hemiacetal to lactone. (A) Three-dimensional rendering of syn-pimaradiene (1) indicating the proximity of known 3β position targeted by SDRs and C19 requiring oxidation in syn-pimaradien-19,6β-hemiacetal (9). (B)–(D) GC–MS analysis of in vitro assays with 9. (B) Chromatogram of OsMS1 catalyzed oxidation to syn-pimaradien-19,6β-olide (10). (C) Mass spectrum of 10, along with the corresponding chemical structure, as determined by NMR. (D) Chromatogram of the negative control reaction (* indicates degradation products of 9 that are particularly prevalent following incubation in aqueous solution—e.g. these are present in much smaller amounts in the originally purified 9—see Figure 5, C).