F. Bottari

Aliphatic and triterpenoid hydrocarbons from ferns

A detailed analysis of the hydrocarbon fractions from the extracts of 21 ferns belonging to 13 families was carried out. n-Alkanes from C24 to C35 and triterpenoid hydrocarbons of the hopane series were identified. The taxonomic value of these results is discussed.

New methods for the preparation of 1-phenyl-trans-cyclohexane-1,2-diol

Abstract In contrast with previous reports, it was found that the reaction of 1-phenylcyclohexene with peroxyformic acid is not entirely stereospecific, but gives some trans -1-phenylcyclohexane-1, 2-diol (IV) beside the cis -isomer (III). The reaction of 1-phenylcyclohexene oxide (II) with formic acid yielded a similar mixture of III and IV, while addition of trichloroacetic acid in benzene was entirely cis -stereospecific. Reaction of the epoxide II with potassium hydroxide took place only under very drastic conditions to give a small yield of III, while sodium 2-dimethylaminoethoxide added exclusively in a trans way, leading to the amino ether X, which was easily transformed into the trans -glycol IV. The latter compound was also the main product of the borohydride reduction of 2-hydroxy-2-phenylcyclohexanone (IX). Possible explanations of the observed stereochemical results are discussed.

A new method for determining the diffusion coefficient of drugs in semisolid vehicles from release data

Abstract Experimental data on release of benzocaine from a series of hydrophilic gels were used for the evaluation of a new method for determining the diffusion coefficient of drugs in semisolid vehicles. The values of D, the drug diffusivity in the vehicle, and of R, the diffusional resistance of the membrane interposed between releasing and receiving phase, resulted from a fit of the experimental release data to theoretical data generated by numerical analysis of a vehicle-membrane controlled diffusional model. Comparison of the computed D (and R) values with values obtained by different routes, or with literature data, showed the method to be conducive to rather accurate estimates of these parameters, in cases where the requirements of the theoretical model were fulfilled by the experimental system. The results are discussed in terms of validity, accuracy and applicability of the proposed method. Results obtained from systems not complying with the diffusional model are also discussed and evaluated. The computations were executed with the aid of an IBM 370/168 computer.

Structure and stereochemistry of a triterpenoid epoxide from Adiantum capillus-veneris

Abstract A triterpenoid epoxide obtained from Adiantum capillus-veneris has been identified as 3α,4α-epoxyfilicane on the basis of several chemical and physical observations.

Stereochemistry of the ring opening of some stilbazole oxides

Abstract The trans and cis forms of 3- and 4-stillbazole oxide and trans -2-( p -methoxystyryl)pyridine oxide have been prepared from the corresponding stilbazoles, by addition of HClO and HBrO, followed by dehydrohalogenation of the halohydrins with base. The configurations of the epoxides have been confirmed by their NMR spectra. The stereochemistry of the ring opening of the above mentioned compounds with HCl, HBr and CCl 3 COOH has been investigated and compared with that of the similar reactions of the stilbene oxides, very pronounced differences in steric course being observed. The reactions of the stilbazole oxides with the hydrogen halides take place with complete inversion, those with CCl 3 COOH with decreasing degrees of inversion in going from the 2- to the 3- and to the 4-pyridyl derivatives.

Stereochemistry of some derivatives of phenylcyclohexane

Abstract 1-Phenylcyclohexene oxide (I) reacted with hydrogen chloride in chloroform to give only 2-phenyl- cis -2-chlorocyclohexanol (V), while in ethanol a mixture of V and its trans diastereoisomer (IV) were formed. The two diastereoisomeric 1-phenylcyclohexane-1,2-diols were transformed by hydrogen chloride in chloroform into IV and V, with entirely stereospecific reactions involving retention. IV and V were oxidized to 2-chloro-2-phenylcyclohexanone (VI); the compound described in the literature and reported to have the latter constitution was found to be instead cis -2-chloro-6-phenylcyclohexanone (XII). It was transformed, through trans -3-phenyl-1,2-epoxycyclohexane (XV) and the corresponding glycols, into 2-phenyladipic acid. The stereochemistry and the possible mechanisms of the reactions are discussed.

Boron trifluoride-catalysed rearrangements of some tetrasubstituted neotriterpene epoxides—I

Abstract The treatment of A′-neogammacer-17(21)-ene oxide ( 1a ) with BF 3 ·Et 2 O complex in CHCl 3 produces entirely different results from those obtained when the same epoxide is treated with HCl in EtOH: while the protic acid converts the compound into the 15,17(21)-diene ( 2a ), the Lewis acid produces rearrangements in the carbon skeleton, with formation of the 28-nor-21α-methyl-12,17-diene ( 3a ) and of the 22,29,30-trisnor-17α-isopropyl-21-one ( 4a ). The structurally similar 19β,28-epoxy-A-neo-18α-olean-3(5)-ene oxide ( 1b ) behaves in a completely analogous manner.

The direction of ring opening of trans-α-methylstilbene oxide by organic acids

Abstract In the reaction of mesitoic acid with trans-α-methylstilbene oxide the anion adds exclusively to the tertiary carbon atom, to give the hydroxy ester of type III, which also can be prepared from α-methylbenzoin mesitoate with KBH4 and is transformed into the isomeric ester of type V by the action of alkali; the latter ester also being formed by reaction of threo-1,2-diphenyl-1,2-propanediol with mesitoyl chloride. Other acids yields only esters of type V, probably formed from primary products of type III by a rapid acyl group shift. All esters thus prepared belong to the threo series; corresponding erythro esters were prepared for comparison. The reductions of α-methylbenzoin acetate and mesitoate with LiA1H4 produce exclusively threo-1,2-diphenyl-1,2-propanediol, in contrast with the low stereoselectivity of the similar reduction of α-methylbenzoin itself.