Abstract
Guanidines easily react with not only acidic compounds but also electrophiles such as alkyl halides, to form the corresponding stable salts due to effective resonance. Thus, modified guani-dines could be expected to play important roles as chiral auxiliaries in asymmetric synthesis if chi-ral environment is produced in reactive salt intermediates. This article reviews the preparation of modified guanidines and their application to asymmetric synthesis. Reasonable asymmetric induc-tions were observed not only in catalytic but also in stoichiometric asymmetric syntheses. These guanidine-mediated reactions may contribute to development of green chemistry because of their possible uses as recyclable (economically favored) and easily functionalizable (widely applicable) auxiliaries.
