Chemistry of ecteinascidins. Part 2. Preparation of 6'-O-acyl derivatives of stable ecteinascidin and evaluation of cytotoxicity

A large amount of stable ecteinascidin 770 (1b) was isolated from the Thai tunicate, Ecteinascidia thurstoni, which was pretreated with potassium cyanide in buffer solution (pH 7), along with a minor metabolite, ecteinascidin 786 (1c). A number of 6'-O-acyl derivatives 3-19 and three diacetyl derivatives 2a-c of the stable 1b were prepared and evaluated for activity against human tumor cell lines HCT116, QG56, and DU145. Nitrogen-containing heterocyclic ester derivatives such as 12, 13, and 16-19 showed similar in vitro cytotoxicity to 1b, whereas the other derivatives were less cytotoxic than 1b. Furthermore, we discovered that the N-indole-3-carbonyl derivative of ecteinascidin 770 (22) has higher cytotoxicity than 1b.     

Water as an Oxygen Source in the Generation of Mononuclear Nonheme Iron(IV) Oxo Complexes

Give me an “O”! Mononuclear nonheme iron(IV) oxo complexes have been generated using water as an oxygen source and cerium(IV) as an oxidant. The high‐yield oxygenation of organic substrates in this system (see picture, Fe green, O red, N blue, C gray) is catalyzed by iron(II) complexes. The source of oxygen in the iron(IV) oxo complexes and the oxygenated products has been assigned unambiguously by isotopic labeling experiments.

     

In-beam M?ssbauer spectroscopy of 57 Mn implanted into lithium hydride

We measured the temperature dependence of ⁵⁷Fe M?ssbauer spectra obtained after ⁵⁷Mn implantation into polycrystalline LiH with an extremely low implantation dose. Density functional calculations suggested that the Fe atoms were predominantly implanted into both Li and H substitutional sites of the LiH crystal.     

N2 emission-channel change in NO reduction over stepped Pd(211) by angle-resolved desorption

A sharp change in the N₂ emission channel from N₂O(a) → N₂(g) + O(a) to N(a) + N(a) → N₂(g) has been found at around 500 K in a steady-state NO + D₂ reaction over stepped Pd(211) = [(S)3(111) × (100)] by means of angle-resolved desorption. The desorbing N₂ is highly collimated at around 30° off normal toward the step-down direction below about 500 K due to the intermediate N₂O decomposition, whereas, above 500 K, the near normally directed desorption due to the recombination of N(a) is relatively enhanced. The N₂O decomposition channel is promoted when the reaction is carried out with hydrogen (deuterium) and the channel change is accelerated by quick changes of the amounts of surface hydrogen and oxygen (or NO(a)) into the opposite directions, and enhanced nitrogen removal as ammonia on the resultant hydrogen-rich surface. In the steady-state NO + CO reaction, the N₂ emission channel gradually changes above 500 K toward recombination. A model for the off-normal N₂ emission is briefly described.     

X-ray scattering studies of fatty acid films on water and on Cdcl2 solutions

X-ray diffraction methods for Langmuir films on the surface of water are briefly presented, together with recent results for docosanoic acid monolayers on pure water and for eicosanoic acid monolayers on an ionic subphase.