306. Actinomycin. Part III. The reaction of actinomycin with alkali

Abstract

The production and purification of actinomycin B are described. Addition of dilute alkali to an alcoholic solution of actinomycin causes a marked hypsochromic effect which is reversible. The reaction obeys secondorder kinetics and is interpreted as a fission of the oxygen bridge of the phenoxazin-3-one nucleus, giving rise to a highly strained and non-planar quinone anil. The reverse reaction involves two stages ; ring closure and elimination of water. Isatin, another molecule which shows a hypsochromic shift in the spectrum after addition of alkali, is shown to possess spectral characteristics which differ from those of actinomycin in several respects.

Thermodynamics of Synthesis of New Phenoxazine Derivatives

“…3H-phenoxazine 1. Many molecules with antiviral, antibiotic and anticarcinogenic effects have a phenoxazine ring in common [1][2][3]. It has been shown that the tricyclic ring system intercalates between adjacent G-C base pairs inhibiting transcription of RNA polymerase.…”

Semisynthesis of A23187 (calcimycin) analogs. II. Introduction of a methyl group on the benzoxazole ring.

“…Compound 10a, which participates in the structure of the actinomycins was prepared according to ANGYAL et a1. 14). The preparation of 10b is described in Scheme 2, the free hydroxylamine 8 underwent rearrangement with TsCI/NEt3 to give the crystalline tosylate 9 in good yield, from which the aminophenol 10b was easily obtained by sodium naphthalene cleavage in 5a, b, in addition to the parent peak M+ which was always present, the main fragmentations of A2318711)…”

Palladium-Catalyzed Cross-Coupling in the Synthesis of Pyridinyl Boxazomycin C Analogues

“…We first examined whether a triflate compound would be a suitable partner in a Stille cross-coupling reaction. Adapting methods used for the preparation of the parent heterocyclic system, 6 was easily produced by reaction of 5 with 1,1‘-carbonyldiimidazole (CDI) in refluxing THF solution and was then reacted with Tf 2 O in dichloromethane at low temperature (Scheme ) . We found that 7 was produced in the reaction with Tf 2 O but was prone to reversion to 6 during purification, and thus we were unable to isolate it.…”