Oxidation of diaryl, aryl alkyl, and dialkyl thioketones by singlet oxygen generated via self-sensitization and other independent methods yielded the corresponding ketone and sulfine in varying amounts. A zwitterionic/diradical intermediate arising out of the primary interaction of singlet oxygen with the thiocarbonyl chromophore is believed to be the common intermediate for the ketone and sulfine. While closure of the zwitterion/diradical to give 1,2,3-dioxathietane would lead to the ketone, competing oxygen elimination is believed to lead to the sulfine. This partitioning is governed by steric and electronic factors operating on the zwitterionic/diradical intermediate.

Longicaudatine has strong reserpine-like activity, which is different from the activities described by Sandberg et al.18 for fractionated extracts of S. longicaudata. Experimental SectionLongicaudatine (1): mp 350 °C dec; [a]D +141°( c 0.5, CHC13); UV 223 nm (log t 4.66), 270 (sh), 284 (4.28), 290 (4.26), 307 (sh, 3.97); in perchloric acid a strong absorption maximum appears at 268 nm; IR (KBr) 3420, 2900,1630,1600,1480, 740 cm"1. The 400-MHz 1H NMR spectrum was recorded in CDC13 on material containing 0.25 molecule of acetone of crystallization (Table I). 13C NMR spectra were recorded at 62 and 25.15 MHz, in CDC13. Proton-noise-decoupled, off-resonance-decoupled, and selective decoupled (¿ 9.6,6.06, and 4.27 in the NMR spectrum) spectra were determined (see Table II). On TLC plates a blue color is obtained with the spray reagents 0.2 M iron(III) chloride in 35% aqueous perchloric acid and 1% cerium(IV) sulfate in 10% aqueous sulfuric acid.

No abstract

No abstract

No abstract