Phthalides optically active

Solid-state photochemical di-ir-methane-type rearrangement of chiral crystals of 43 have been found to give a mixture of 44 of 44% ee and 45 of 96% ee [25]. When chiral crystals of the thioester 46 were irradiated at 0°C for 6 hr, optically active phthalide 47 of 30% ee was obtained in 65% yield [26],... 

The second example is photochemical reaction of 2-benzoylbenzothioesters 57 in the chiral crystalline environment. Solid-state photoreactions of, S -(o-tolyl),. S -phcnyl, and S-(ff)-tolyl) 2-benzoylbenzothioates 57a-c, which formed chiral crystals by spontaneous resolution, underwent an intramolecular cyclization involving phenyl migration to afford the corresponding optically active 3-phenyl-3-(arylthio)phthalide 58a-c in good chemo- and enantio-selectivities. (Scheme 11). [34]... 

The sequence can be extended to preparation of optically active phthalides... 

These intramolecular cyclization reactions in the solid state were also examined with other thioesters 51d g to give the corresponding phthalides 52d-g, but as racemates. The failure of generation of optical activity in the products was well compatible with their centrosymmetric crystal systems such as Pljc and Pi. 

N,A-Disubstituted 2-benzoylbenzamides 106 also formed chiral crystals in space group P212121. Irradiation of these crystals gave optically active phthalides 107 in high optical and chemical yields [97]. It was concluded from the x-ray structural analysis that the photoreaction promoted intramolecular cyclization to phthalides via a radical pair intermediate, not phenyl migration. 

NOSCAPINE (NARCOTINE) As an optically active, laevorotatory substance noscapine is found in opium (2-12%). This alkaloid is, next to morphine, the most plentiful of the opium alkaloids. Structurally it differs from the phenanthrene derivatives morphine and codeine by its phthalide isoquinoline— skeleton. 

The greatest advantage of this approach is the circumvention of the use of optically active tertiary propargylic alcohols. The chiral Rh complex could efficiently desymmetrize the achiral alcohol to give the 3,3-disubstituted phthalides products in up to 87% isolated yield and 93% ee. The kinetic resolution of racemic tertiary propargylic alcohols provided disubstituted phthalides with up to 89% 3deld and up to 93% ee. 

Two syntheses of hongconin (18), a naturally occurring isochroman-4-one which exhibits antianginal activity, have been described. One utilises the annulation of phthalide unit to optically pure dihydropyran-3-ones <96JOC455>, whilst a similar Michael addition to the bicyclic pyranone levo ucosenone and subsequent enolate methylation are essentials of the second route <96JOC459>. 

---