ChemInform Abstract: AZASTEROIDE AUS 3BETA‐CHLOR‐5ALPHA‐CHOLESTANON‐(6) UND 3BETA‐ACETOXYCHOLESTEN‐(4)‐ON‐(6)

Abstract

Durch Schmidt‐Reaktion des Ketons (Ia) bzw. Beckmann‐Reaktion des Oxims (Ib) entsteht das Lactam (II).

Lathyranoic Acid A: First Secolathyrane Diterpenoid in Nature fromEuphorbia lathyris

“…The complex i could be further transformed to a key intermediate ( ii ) by a mechanism similar to that of the chemical Baeyer−Villiger oxidation, and the orientation of C-15-OH must be retained during the migration. The insertion of oxygen could occur between C-14 and C-15 because the fully substituted C-15 carbon has a migratory aptitude comparable to that of the vinyl group …”

“…IR absorptions at 3419-2500, 1747, 1716, 1680, and 1635 cm -1 implied the existence of carboxyl, acyl, and ketone groups and double bonds, respectively. The 1 H NMR, 13 C NMR (Table 1), and DEPT spectra indicated, besides signals attributable to one acetyl group and one benzoyl group, the presence of a ketone group, a carboxyl group, three double bonds (one exocyclic and two trisubstituted), and 12 sp 3 carbons, including four methyls, two methylenes, five methines (two oxygenated), and one quaternary carbon. The above functionalities accounted for 11 degrees of unsaturation, and the remaining two degrees of unsaturation required the presence of two additional rings in lathyranoic acid A (1).…”

“…Two subunits a (C-1 to C-3; C-16) and b (C-7 to C-9; C-11 to C-12) (Figure 1), drawn with bold bonds, were established on the basis of 1 H-1 H COSY data. The HMBC correlations (Figure 1 The relative stereochemistry of lathyranoic acid A (1) was partially assessed by analysis of its 13 C NMR and NOESY data (Figure 2). The upfield-shifted carbon signal of C-20 at δ 12.3 revealed an (E)-geometry for the ∆ 12 double bond, 9 which was confirmed by a NOESY correlation between H 3 -20 and H-11.…”

“…Fractions 3 and 4 were chromatographed on silica gel columns (petroleum ether/EtOAc ) 10:1) to obtain two major compounds, each of which was then purified on a RP-18 column (75% MeOH in H2O) to give lathyranoic acid A (1) (0.0005%) and Euphorbia factor L11 (2) (0.011%), respectively. Lathyranoic acid A (1): colorless amorphous solid; mp 57-58 °C; [R] 20 D -27°(c 0.67, CHCl3); UV (MeOH) λmax (log ) 230 (4.50); IR (KBr) νmax 3419-2500, 2958, 2926, 1747, 1716, 1680, 1635, 1452, 1375, 1271, 1230, 1111, 1026, 714 cm -1 ; 1 H and 13 C NMR data, see observed in the 1 H NMR (Table 1), 39 were assigned to the bonding carbons by analysis of the HMQC spectrum. The only remaining signal at δ 4.24 was assumed to be the proton signal of a hydroxyl group (IR absorption at 3435 cm -1 ).…”

“…Thus, the planar structure of 2 was established as shown in Figure 1. The relative configuration of 2 was determined by analysis of its 13 C NMR and NOESY spectra (Figure 2) and by comparison with the literature data of this compound class. The upfield-shifted carbon signal of C-20 at δ 14.0 revealed an (E)-geometry for the ∆ 12 double bond, 9 and this was confirmed by a NOESY correlation between H 3 -20 and H-11.…”