Ruthenium-Catalyzed Rearrangement of ent-14-(Benzoyloxy)-15,16-epoxybeyerane Diterpenes

Abstract

Rearrangements of ent-18-acetoxy-14α-(benzoyloxy)-15α,16α-epoxybeyerane and ent-18-acetoxy-14β-(benzoyloxy)-15α,16α-epoxybeyerane, catalyzed by ruthenium acetylacetonate, were carried out. With the 14-endo-(benzoyloxy) compound, ent-18-acetoxy-14α-(benzoyloxy)beyera-9,15-diene, ent-18-acetoxy-15α-(benzoyloxy)-14α-hydroxykaur-16-ene, ent-18-acetoxy-15α-(benzoyloxy)-14α-hydroxy-(16S)-kaur-11-ene, and ent-18-acetoxy-14α-hydroxy-(16R)-kauran-15-one were isolated. However, rearrangement of the 14-exo-(benzoyloxy) compound gave ent-18-acetoxy-15β-(benzoyloxy)-14α-hydroxykaur-16-ene, ent-18-acetoxy-15β-(benzoyloxy)-14α-hydroxyatis-16-ene, ent-18-acetoxy-14β-(benzoyloxy)-16β-chloro-15α-hydroxybeyerane, ent-18-acetoxy-15β-benzoyloxy)-14α-hydroxy-(16S)-kaur-11-ene, ent-18-acetoxy-15β-(benzoyloxy)-12α-chloro-14α-hydroxy-(16S)-kaurane, and ent-18-acetoxy-14β-(benzoyloxy)-12α-chloro-15α-hydroxybeyerane. The influence of the C-14 benzoyloxy substituent and its arrangement are discussed by comparison with other rearrangement processes reported previously.

Diterpenoids

“…The ruthenium-catalysed rearrangement of ent-14-(benzoyloxy)-15,16-epoxybeyerane to compounds of the kaurene series has been explored. 123 The atiserene skeleton has been assigned 124 to the lactone spiramilactone 104, obtained from Spirea japonica. The production of scopadulcic acid 105 by tissue cultures of Scoparia dulcis (Scrophulariaceae) and its inhibitory effect on bone resorption as well as its antiviral and antitumour activity have been examined.…”

The First Atisane Diterpenoids from a Liverwort: Polyols from Lepidolaena clavigera

“…Compounds 1 and 2 are the first atisanes reported from liverworts 1 and the most oxygenated naturally occurring compounds with this skeleton. The most oxygenated atisane that we could find previously reported was a triol derivative ,, …”

“…The most oxygenated atisane that we could find previously reported was a triol derivative. 13 Hexaol and pentaol derivatives 1 and 2 continue the pattern of highly oxygenated bioactive terpenoids in the genus Lepidolaena. 2,6,7 The less polar atisane 2 showed slight cytotoxic activity against mouse leukemia cells (P388 IC 50 16 µg/mL) 2 and moderate insecticidal activity against blow fly larvae.…”

“…A second entry point was provided by the CH (H14, Table 1) correlated to the other acetate carbonyl, which showed vicinal 1 H-1 H couplings to a CH 2 (H14/H13). 1 H- 13 C correlation between the 14CH and a quaternary C (H14/C8), an oxygenated CH (H14/C15) and a CH 2 (H14/C7) established sub-structure C (Figure 1). The CH at 69.4 ppm (C15) correlated with the exocyclic methylene protons (C15/H17), as did another CH (C12/H17), extending the connectivity to sub-structure D.…”

Skeletal Rearrangements of Rings C and D of the Kaurene and Beyerene Tetracyclic Diterpenoids

“…Thus the ruthenium acetonylacetonate-catalysed rearrangement of ent-14-(benzoyloxy)-15,16-epoxybeyeranes led to a range of kaurene derivatives. 30 The Wagner-Meerwein rearrangement of steviol-16,17-epoxide gave a 17-hydroxybeyeran-16-one analogue of isosteviol. 31 However, the presence of a second hydroxyl group at C-15 prevented this reaction.…”