The garryfoline–cuauchichicine rearrangement: a study of the mechanism in the (–)-kaurenols

Abstract

The mechanism of the garryfoline-cuauchichicine rearrangement has been investigated using the epimeric (-)kaur-16-en-15-ols as models. The 15s-01 is shown to rearrange rapidly in mineral acid at room temperature to 16R-(-)-kaur-l5-one by a 15,16-hydride shift. The 16a-01, like veatchine, is stable under these conditions.The contrast in the ability of these epimeric alcohols to undergo 15,16-hydride shifts is discussed.Under the same conditions, (-)-kaur-l5-en-I 7-01 gives the allylic isomer, (-)-kaur-l6-en-I 5a-01, but, under more forcing conditions, it yields 16S-( -)-kauran-l7-al.THE diterpene alkaloid, garryfoline (I), is rapidly rearranged to cuauchichicine (11) in dilute mineral acid at room temperature. A similar rearrangement has been observed in the diterpene alkaloids , napelline ,2 kobusineJ3 and atisine,* and recently in the (-)-kaurene derivative (VII; R = H, 19-C0,H).5 The generality of the rearrangement has been demonstrated with the monocyclic allylic alcohols (111; n = 1 or 2) and (IV; n = 1 or 2) which, under more forcing conditions in the presence of 2,4-dinitrophenylhydrazine, gave the DNP derivatives of the ketones (V; n = 1 or 2).

Hydrogen bonding in ferrocene derivatives: structure of the 1:1 adduct of ferrocenyl(diphenyl)methanol and dimethyl sulfoxide

“…Within the ferrocenyl moiety, the C--C bond lengths in the substituted cyclopentadienyl ring range from 1.403 (4) to 1.426 (3) A [mean 1.420 (3) A] while those in the unsubstituted ring lie in the range 1.384 (5) to 1.411 (6),~, [mean 1.397 (5),4,]. Such differences between the substituted and unsubstituted rings have been noted previously (Barnes, Bell, Glidewell & Howie, 1990). The other interatomic distances within the ferrocenc fragment are typical of their types.…”

Ferrocenyl hetaryl thioketones: A computational study of their conformational stability

“…The survey revealed that there is only one crystal structure possessing any of the investigated thioketones. In this structure (refcode: JEPVIJ [48] ), thioketone 5 acts as a ligand to Cr(CO) 4 the Fc substituent are rotated by 18.1 , which points to its in-between conformation, neither eclipsed nor staggered. The τ Ph value of 5 is very close to one of the τ Ph angles measured for the crystal structure of diphenyl thioketone (τ Ph = 317.4 and 328.1 ; refcode: THBZPS10 [49] ).…”

Spontaneous polymerization of methyl methacrylate in aqueous sulfuric acid

“…Therefore, the effect of oxygen in this polymerization is twofold: on the one hand, it generates peroxides (so creating the species responsible for polymerization); on the other hand it tends to inhibit the polymerization .through addition to the monomer. 5 The amount of peroxides present in the monomer also has a great influence on the intrinsic viscosities. Experiments in which H2SO4 was replaced by HC104 or HCl were negative, indicating that the mechanism of initiation involves the participation of the sulfuric moiety of the acid.…”