Oh

Scheme 69

The ipecac alkaloid emetine (242), used as antiamebic, is degraded when the dihydrochloride is irradiated in aqueous solution. The observed paths include oxidative cleavage of the methylene bridge between the two heterocyclic rings to give products (243) and (244) as well as oxidation to immonium salt (245) and oxidative cyclisation to (246) (Scheme 69).229

Antimicotics are another class of drugs where many photoreactive compounds are found, among both drugs for systemic and for topical use. A review of recent results in this field is presented by K. Thoma in this book (p. 116).

2.6.6 Antineoplastic Drugs. The yellow antineoplastic cisplatin (247) is solvated by irradiation in aqueous solution and the rate of the process depends on the pH.230> 231 The products characterised have been the c/s-diamineaquochloro complex (248) in the absence,232 and the aminetrichloro complex (249) in the presence of sodium chloride (Scheme 70). 23 ^

Scheme 70

The nitroso ureides carmustine (250)234 and tauromustine (251)235 are light sensitive, as it is the case for mitonaftide (252)236 The antitumor alkaloid vinblastine sulfate (253) is both thermally and photochemically unstable.237

6-Mercaptopurine (38) is oxidised when irradiated in oxygen-equilibrated aqueous solution by near-uv light, giving as the primary product the sulfonate (254), which is then further oxidised to the sulfonate (255) (Scheme 71).238

SO,H

SO,H

H (254) Scheme 71

SChH

H (254) Scheme 71

SChH

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