1,5-Asymmetric induction in boron-mediated aldol reactions of beta-oxygenated methyl ketones.
This tutorial review describes that high levels of substrate-controlled, 1,5-stereoinduction are obtained in the boron-mediated aldol reactions of beta-oxygenated methyl ketones with achiral and chiral aldehydes. Remote induction from the boron enolates gives the 1,5-anti adducts, with the enolate pi-facial selectivity critically dependent upon the nature of the beta-alkoxy protecting group. This 1,5-anti aldol methodology has been strategically employed in the total synthesis of several natural products with remarkable pharmacological activities. At present, the origin of the high level of 1,5-anti induction obtained with the boron enolates is unclear, although a model based on hydrogen bonding between the beta-alkoxy oxygen and the formyl aldehyde hydrogen has recently been proposed.
Dias
Luiz C
LC
Instituto de Química, Universidade Estadual de Campinas, UNICAMP, C. P. 6154, CEP 13084-971, Campinas, SP, Brazil. ldias@iqm.unicamp.br
Aguilar
Andrea M
AM
D000447:Aldehydes / Q000737:chemistry*; D001688:Biological Products / Q000737:chemistry; D001895:Boron / Q000737:chemistry*; D006860:Hydrogen Bonding; D007659:Ketones / Q000737:chemistry*; D013237:Stereoisomerism
D000447:Aldehydes; D001688:Biological Products; D007659:Ketones; D001895:Boron