The comparison of the synthetic compound with the nominal identical compound isolated by Doorenbos and colleagues showed the two materials were not the same. John, N.B.) and colleagues, who had previously described the total synthesis of (±)-stemarin ( 8) ( vide infra), and Manchand, in the frame of their work on stemodane diterpenes, described the preparation of (±)-stemodinol ( 4). , and published in the same year, in which the isolation, X-ray structure and absolute configuration determination of (+)-stemarin ( 8), “a diterpene with a new skeleton” isolated, along with (+)-2-deoxystemodinone ( 6), from S. 1975, Manchand and colleagues submitted the paper to J. at the end of March 1975 and was accepted for publication on Feb. The paper by Doorenbos and colleagues was submitted to the J. maritima and structure elucidation of which had been reported by Manchand and Blount in 1975. 183–184 ☌, d = +17.8), a structural diastereoisomer with a new and unique skeleton, the isolation from S. Some years later ( vide infra), it was, in fact, demonstrated that the structure (+)- 4 had been erroneously attributed to (+)-stemodinol and that the true structure of the latter was that of (+)-stemarin ( 8) (m.p. Unfortunately, the comparison was misleading. This resulting material was “identical in all respects” with (+)-2-deoxystemodinone ( 6), previously obtained from (+)- 2 and (+)- 3 ( vide supra), thus confirming the stemodane skeleton and the HO–C(13). In order to confirm the stemodane skeleton, (+)- 4 was oxidized to 7 ( D not reported as in all cases where the rotation sign is not given) and the latter deoxygenated by the Huang–Minlon procedure to (+)- 6. The 1H-NMR spectra revealed the presence of a primary alcohol function that was located at C(18) on the basis of a detailed 1H-NMR analysis.
182–183 ☌, d = +13.8) was carried out by means of chemical work (highlighted below, Scheme 2), IR and 1H-NMR. The investigation on this new diterpenoid (m.p. The same group then addressed the structure elucidation work of what was supposed to be (+)-stemodinol ( 4). No other location of the carbonyl group could have accommodated such unsaturated functions ( 5c or 5d) within the molecule ( Figure 5). It followed that the carbonyl should have been located at C(1) or at C(3). The location of the secondary hydroxy group followed the observation that (−)- 5 could be converted into an α,β-unsaturated ketone. Thus, (+)- 3, the molecular formula, IR and 1H-NMR, of which revealed the absence of unsaturations and the presence of four cycles and two hydroxyls, was oxidized to (−)- 5 and the latter deoxygenated by the Huang–Minlon procedure to give known (+)-2-deoxystemodinone ( 6), thus confirming the stemodane skeleton ( Figure 1), the C–(13) substitution and the presence of a secondary hydroxyl ( Scheme 1). The structure of (+)- 3 was deduced by means of chemical work (highlighted below), IR and 1H-NMR. maritima, collected in the Caribbean island of Curaçao, along with (+)- 1 and (+)- 2, of (+)-maritimol ( 3) and what was supposed to be (+)-stemodinol ( 4) (vide infra). Guerrero, the isolation from the aboveground portion of S. Doorenbos (University of Mississippi), reported, in collaboration with C.D. From it followed that of (+)-stemodin ( 1).Ī few years later, in 1976, N.J. The (+)-stemodinone ( 2) absolute configuration was attributed on the basis of its positive ORD Cotton effect. Vicinal coupling of H–C(2) in (+)-stemodin ( 1).
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