Phenethyl group

Table 3.12 surveys current industrial applications of enantioselective homogeneous catalysis in fine chemicals production. Most chiral catalyst in Table 3.12 have chiral phosphine ligands (see Fig. 3.54). The DIP AMP ligand, which is used in the production of L-Dopa, one of the first chiral syntheses, possesses phosphorus chirality, (see also Section 4.5.8.1) A number of commercial processes use the BINAP ligand, which has axial chirality. The PNNP ligand, on the other hand, has its chirality centred on the a-phenethyl groups two atoms removed from the phosphorus atoms, which bind to the rhodium ion. Nevertheless, good enantio.selectivity is obtained with this catalyst in the synthesis of L-phenylalanine. 

Gutierrez-Garcia, V. M. Lopez-Ruiz, H. Reyes-Rangel, G. Juaristi, E. Enantioselective synthesis of / -amino acids. Part 11. Diastereo-selective alkylation of chiral derivatives of /J-aminopropionic acid containing the jS-phenethyl group. Tetrahedron 2001, 57, 6487-6496. 

K. Chemoselective debenzylation of the N-l-phenethyl group in 2-oxazolidinones by the anisole-MeSOsH system. Heterocycles 2002,... 

The protease X-ray crystal structure of 34 showed that the a-ethyl and the a-phenyl groups were bound in the SI and S2 sites, respectively, and that the phenethyl group was positioned near the S2 pocket. Compound 35 was then designed with the aim of gaining additional binding by placing a second ethyl group in the ST site [71]. This compound was tested as a mixture of four stereoisomers and exhibited a 13-fold increase in potency relative to 34. 

Amides 113-115 are especially attractive, since the unsaturated chain, cyclic enone, and removable chiral auxiliary such as an a-phenethyl substituent are simultaneously attached to the nitrogen atom. However, the allylic or benzylic hydrogen atoms present in the starting molecule allow competitive hydrogen abstraction processes. In the presence of an a-phenethyl group, cycloadducts were indeed isolated but in low yields and poor diastereomeric excess, besides rearranged products [75]. 

Introduction of at least one fluorine atom to the methyl group of acetophenone leads to a dramatic change in configurational preference of the corresponding N-( l-phenethyl)imines (16, 17, and 18) from syn to anti, where the syn configuration of the methyl group to the N-phenethyl group is preferred in the parent nonfluorinated imine 15 (Scheme 1.79) [15]. The stereochemistry was confirmed by NOE analysis in H NMR for 16 and 17, and... 

A series of 6-alkyl derivatives was prepared as summarized in Table 13. In the first series (103-106), the phenethyl group was substituted with a 4-OH group and the C-3 aryl moiety contained the benzyl alcohol substituent while the C-6 group was varied. When the aryl group was replaced with the isosteric cyclohexyl moiety (103), no significant change in enzyme activity was noted. However, the cellular antiviral potency increased dramatically when compared to the C-6 phenyl analogue (95)—a ninefold increase in efficacy. Similar results were obtained... 

---