Asymmetric ortho-deprotonation of (η6-arene) chromium tricarbonyl complexes substituted with a chiral hydroxylamine

The use of O-methyl-N-(α-methylbenzyl)hydroxylamine as a novel chiral auxiliary in asymmetric ortho-deprotonation of the (η6-arene) chromium tricarbonyl complexes is described. Upon quenching of the resultant ortho-lithiated complex with an electrophile, 1,2-disubstituted (η6-arene) chromium tricarbonyl complexes were obtained in good yield and excellent levels of diastereoselectivity

Synthesis of (R)-{eta(6)-[O-methyl-N-(alpha-methylbenzyl)hydroxyamino]-benzene} chromium tricarbonyl via nucleophilic aromatic substitution of (eta(6)-fluorobenzene) chromium tricarbonyl

Chiral hydroxylamine chromium tricarbonyl complexes may be prepared in satisfactory to reasonable yieldvia nucleophilic aromatic substitution of the anion derived from N,O-substituted hydroxylamines and (η6-fluorobenzene) chromium tricarbonyl. The enantiomerically pure complex (R)-{η6-[O-methyl-N-(α-methylbenzyl)hydroxyamino]- benzene} chromium tricarbonyl 6a was characterised by X-ray crystallography

Asymmetric synthesis of secondary benzylic alcohols via arene chromium tricarbonyl complexes

(Aryl aldehyde)- and (aryl ketone)-chromium tricarbonyl complexes ortho-substituted with the chiral auxiliary O-methyl-N-(α-methylbenzyl)hydroxylamine undergo diastereoselective addition of Grignard reagents and Super-Hydride®, respectively, to give the corresponding secondary alcohols in high diastereoisomeric purity. These compounds may be easily decomplexed and deprotected to give the corresponding enantiopure amino alcohols

Asymmetric synthesis of secondary benzylic alcohols via arene chromium tricarbonyl complexes

(Aryl aldehyde)- and (aryl ketone)-chromium tricarbonyl complexes ortho-substituted with the chiral auxiliary O-methyl-N-(α-methylbenzyl)hydroxylamine undergo diastereoselective addition of Grignard reagents and Super-Hydride®, respectively, to give the corresponding secondary alcohols in high diastereoisomeric purity. These compounds may be easily decomplexed and deprotected to give the corresponding enantiopure amino alcohols

Asymmetric ortho-deprotonation of (η6-arene) chromium tricarbonyl complexes substituted with a chiral hydroxylamine

The use of O-methyl-N-(α-methylbenzyl)hydroxylamine as a novel chiral auxiliary in asymmetric ortho-deprotonation of the (η6-arene) chromium tricarbonyl complexes is described. Upon quenching of the resultant ortho-lithiated complex with an electrophile, 1,2-disubstituted (η6-arene) chromium tricarbonyl complexes were obtained in good yield and excellent levels of diastereoselectivity

Synthesis and evaluation as bioactive compounds

Catechols from abietic acid were prepared by a short and good yielding chemical process and further evaluated for several biological activities namely, antifungal, antitumoral, antimutagenic, antiviral, antiproliferative and inhibition of nitric oxide. Their properties were compared with those of carnosic acid (6), a naturally occurring catechol with an abietane skeleton and known to possess potent antioxidant activity, as well as anticancer and antiviral properties. From all the synthetic catechols tested compound 2 showed the best activities, stronger than carnosic acid. (C) 2003 Elsevier Science Ltd. All rights reserved