Intramolecular Photochemical [2+2] Cycloadditions of Enantiomerically Pure 4,4-Disubstituted Cyclohexenones: An Approach to the Total Asymmetric Synthesis of Lintenone

Biradical to biradical rearrangement via 1,3-H atom transfer in photocycloisomerizations of 4-pent-4-enylcyclohex-2-enones

“…This same tricyclodecanone skeleton is also found in the sesquiterpene (Ϫ)Lintenone, isolated from a marine sponge. 7 The trans-fusion of the two six membered rings in 14, and 16 in contrast to the cis-fusion in 12 is also evidenced by NMR data. In the 13 C NMR spectra the ring junction carbon chemical shifts for a trans ring junction are generally greater than those for a cis junction by approximately 8-10 ppm, 8 and in the 1 H NMR spectra both the large vicinal coupling constant for the bridgehead H atoms, 3 J ≈ 12.5 Hz as well as the relatively small geminal coupling constant for the methylene protons next to the CO group, 2 J ≈ 14.5 Hz, are again indicative for such a steric pattern.…”

Enantiomerically Pure Cyclobutane Derivatives and Their Use in Organic Synthesis

“…Although π-facial selectivity for reaction of the conjugated alkene is excellent, that for the isolated alkene in the alkyl-substituted derivatives of 46 is low. 33 An interesting chiral-induced intramolecular photocyclization followed by a cascade of thermally and photochemically induced isomerizations were reported for the chiral auxiliary substituted acetophenones 48. The initially formed tricyclic cyclobutane is transformed by tandem thermal and photo- chemical steps involving concerted electrocyclizations to give the chiral cyclobutenes 49 as end products with de's ranging from 15% to 90% depending on the nature of the chiral auxiliary (Scheme 15).…”

“…The optically pure cyclohexenone 46 undergoes intramolecular cycloaddition to give the tricyclic ketones 47 in yields of 95−99% (Scheme ). Although π-facial selectivity for reaction of the conjugated alkene is excellent, that for the isolated alkene in the alkyl-substituted derivatives of 46 is low 14 …”

Synthesis of (+)-Sulcatine G

“…Counting sulcatine G, there are 16 skeletal classes of natural products containing this unusual structure . The four others that have drawn the efforts of synthetic chemists are 2-isopropylidene-3b,6a-dimethyl-octahydro-cyclobutadicyclopenten-1-one, lintenone, solanoeclepin A, and 3-debromoperforatone …”