RESUMO
A series of chiral oxovanadium(IV) complexes derived from tridentate N-3,5-substituted and N-3,4-benzo- and N-5,6-benzo-salicylidene-alpha-amino acids can serve as efficient catalysts for the enantioselective oxidative couplings of various 3-, 6-, and 7-substituted 2-naphthols under O(2). The best scenario involves the use of a vanadyl complex arising from 2-hydroxy-1-naphthaldehyde and valine (or phenylalanine) in CCl(4), leading to BINOLs in good yields (75-100%) and with enantioselectivities of up to 68%.
RESUMO
[reaction--see text] Among four vanadyl species examined, vanadyl triflate was the most efficient catalyst to facilitate nucleophilic acyl substitution of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. By using mixed-anhydride technique, one can achieve oleate and peptide syntheses. In marked contrast to common metal triflates, the amphoteric character of the V=O unit in vanadyl species was proven to be responsible for the catalytic profile in this process.
RESUMO
A series of benzyl propargyl ethers were synthesized and tested as inhibitors of 5-lipoxygenase, the key enzyme involved in leukotriene biosynthesis. Among these, optimum activity was displayed by 1-(2-heptynyloxymethyl) benzene 12 (IC50 1.2 microM). Addition of carboxyl group at the end of the alkyl side chain attached to the acetylenic group abolished the inhibition. Selective reduction of the acetylenic group to cis or trans double bond reduced the inhibitory potential, the cis isomer 24 showing more than 20-fold higher inhibition than the trans isomer 25. Introduction of sulphur in place of oxygen in the alkyl side chain attached to the (carboxyalkyl) benzyl group also reduced the inhibition. The IC50 value of 12, towards rabbit reticulocyte 15-LOX is > 50 fold higher than that of 5-LOX. These results indicate that compound 12 is a specific inhibitor of 5-LOX.