Alkene–Arene meta Photocycloadditions with a Four‐Carbon‐Atom Tether: Efficient Approach toward the Polycyclic Ring Systems of Aphidicolin and Stemodinone

The arene–alkene photocycloaddition

“…The first intramolecular meta photocycloaddition was reported in 1969 by Morrison and Ferree [ 39 ]. The intramolecular reaction was shown to be very efficient when three atoms tethers were employed, but the quantum yield drops considerably when four atoms tethers are involved [ 40 ], apart from some exceptional cases when the freedom of the tether is restricted and a suitable conformation can be found [ 41 ]. The influence of the incorporation of oxygen in the tether has been reviewed by de Keukeleire [ 42 ].…”

The Chemistry of Bioactive Diterpenes

“…The extract was dried, concentrated and set aside to crystallize. This diterpene and its prodrugs show good activity against a range of tumor types [13], and leishmanial parasities [14]. There exists evidence that selective inhibition of DNA polymerase-activity is the principle cause for the prevention of cell division by aphidicolin in sea urchin embryos [11].…”

Organic photochemistry

“…The use of photocycloaddition between arene-alkene systems achieved the efficient synthesis of polycyclic ring compounds. 2 In particular this offers a means of preparing ring systems based on the biologically active aphidocolin and stemodinone systems. Irradiation of the alkene and arene substrates gave regioselective cycloaddition to form cyclopropane bridged polycyclic ring systems.…”

“…Solvent effects were also reported for the irradiation of 2-(alkoxymethyl)-5methyl-(R)-chloroacetophenones 1a-c and 2-(methoxymethyl)-5-methylphenacyl benzoate 1d in dry, non-nucleophilic solvents (Scheme 1). The reaction produced 3-alkoxy-6-methylindan-1-ones (3a-c) in very high yields, 4 although a competing product, 3-methylisobenzofuran-1(3H)-one (2), was isolated as a major photoproduct when trace amounts of water were present. Quenching and laser flash spectroscopy experiments were carried out and indicated that the indanone derivatives 3 (which dominate in 'dry' solvent) result from 1,5-hydrogen migration from the lowest triplet excited state of the acetophenones 1 and this is followed by cyclization of the resulting photoenols.…”