Asymmetric Induction by the Cholestanic Moiety on Tropos Species:  Synthesis and Stereochemical Characterization of Bile Acid-Based Biphenyl Phosphites

Abstract

Three different bile acid-derived biphenyl phosphites were synthesized, starting from cholic and deoxycholic acids and biphenol, and their stereochemical features were checked by CD and NMR spectroscopies. On the basis of the spectroscopic results, the capability of the cholestanic system to induce a prevalent sense of twist on the biphenyl moiety of the bile acid-derived phosphites as well as their tropos nature was inferred.

Bile Acid Derived Tropos Vaulted Bi­naphth­ylphosphites: Synthesis, Stereo­chemical Characterization and Complexation to Rhodium

“…The similarity of the spectra, as far as sign and position of the Cotton effects are concerned, and the presence of a negative exciton couplet centered at 202 nm indicates that the sense of twist of the binaphthyl moiety is also M for phosphites 4 and 5 , whereas the different amplitude13 of the couplet in passing from one phosphite to another suggests that the extent of the screw sense prevalence is different, being highest in phosphite 6 and lowest in phosphite 5 . Therefore, the three different positions of bile acids induce the same sense of twist to the vaulted binaphthylphosphite moiety, unlike what is observed in the case of biphenylphosphites, for which a different sense of twist is found in passing from 12‐biphenylphosphite ( M ) to 7‐biphenylphosphite ( P ) 4a. Another difference is the higher prevalence of the sense of twist for the 7‐binaphthylphosphite, whereas in the case of biphenylphosphites the same extent of the prevalence was observed for both 7‐ and 12‐derivatives 4a…”

“…Therefore, the three different positions of bile acids induce the same sense of twist to the vaulted binaphthylphosphite moiety, unlike what is observed in the case of biphenylphosphites, for which a different sense of twist is found in passing from 12‐biphenylphosphite ( M ) to 7‐biphenylphosphite ( P ) 4a. Another difference is the higher prevalence of the sense of twist for the 7‐binaphthylphosphite, whereas in the case of biphenylphosphites the same extent of the prevalence was observed for both 7‐ and 12‐derivatives 4a…”

“…Binaphthol 3 was then obtained quantitatively by deprotection of the hydroxyl groups with BBr 3 in dichloromethane solution at room temperature. To synthesize phosphites 4 – 6 , two different derivatives 10 and 11 of deoxycholic acid, possessing free OH groups at positions 12 and 3, respectively, and methyl 3,12‐diacetyloxycholate ( 12 ), were prepared by known procedures 4a. By reacting binaphthol 3 and PCl 3 in the presence of triethylamine, the corresponding binaphthylchlorophosphite was obtained, which was not isolated but instead directly used for the next step.…”

Bile acids in asymmetric synthesis and chiral discrimination

“…39 These findings opened the possibility to obtain a new class of chiral ligands, 12 being an example. Their activity and enantioselectivity were tested in the asymmetric rhodium-catalyzed hydrogenation of dimethylitaconate (Fig.…”

A stereodynamic phosphoramidite ligand derived from 3,3′‐functionalized ortho‐biphenol and its rhodium(I) complex

“…[4][5][6][7][8][9] Related stereodynamic phosphites obtained with chiral alcohols were explored by Iuliano and colleagues, while Reetz and colleagues investigated mixtures of tropos and atropos phosphite ligands. [10][11][12][13][14][15][16][17] RajanBabu and Parquette and colleagues reported the catalytic application of tropos phosphinites bearing chiral dendrimeric substituents. 18 In addition, BIPOL has been used for the design of stereodynamic organocatalysts ( Figure 1A).…”