Typical utility of carbene and carbenoid reactions is the carbon-carbon bond forming reaction which provides a number of convenient and direct tools for molecular construction by manipulating divalent and ambiphilic, , particularly electrophilic nature of carbene-type reactive molecules under controlled conditions. The present review deals with the following topics of carbene reactions reported during 1986-1989, selected mainly from a synthetic viewpoint : (1) vinylcarbenes in equilibrium with cyclopropenes and their addition reactions, (2) carbenes substituted by hetero atom(s) such as O, N, P, and S, (3) electrophilicity of carbenoids and their stereoselective alkylation, (4) mechanism and synthetic application of C-H insertion reactions by carbenes (e.g. alkylidenecarbenes) and carbenoids (e.g. lithium (phenylthio) carbenoid), (5) rhodium-catalyzed reactions of ketocarbenoid with O-H, and N-H bond, (6) novel methods of generating carbenes under neutral and mild conditions.
The phorbol esters belong to the group of natural products based upon the hydrocarbon nucleus known as tigliane. Phorbol esters have been the focus of current synthetic endeavor since these noncarcinogenic compounds amplify the effect of certain carcinogens in animals. This review describes recent progress in the synthetic approach to tiglianes and the first total synthesis of phorbol (1).
Nogalamycin (1) and its congeners are notable members of the anthracycline family because of their promising antitumor activity. Especially, 7-con-O-methylnogarol (2), the semisynthetic derivative of 1, has been selected for clinical trials. This review deals with the first total synthesis of the nogalamycin congeners, (+) - nogarene (3), (+) -7-deoxynogarol (4), (+) -2, and their related compounds. This synthesis involved the stereocontrolled synthesis of the naphthoquinone (44), the CDEF-ring system, and regioselective Diels-Alder reaction of 44 with highly functionalized dienes. Antitumor activity assay of the artificial nogalamycin congeners disclosed novel aspects of the structure-activity relationships.