A new photochromic 8pi-system based on an azaheptatriene-tetrahydroazepinoisoquinoline electrocyclization.

A new photochromic family of tetrahydroazepinoisoquinolines (THAI) 4a-i has been prepared. It undergoes light-induced ring opening from spiro compounds 4 to betaines 3 that decolorize in a very fast cyclizing reaction. Depending on substitution of the precursors 1 and 6, the photochromic styryltetrahydroindolizines (THI) 5k-q are formed in a periselective way. The conformation and configuration of the new photochromic THAI 4 and THI 5 were investigated by NMR and the structure of both compounds was proven by X-ray analysis. The photochromic properties were studied by laser flash photolysis, which afforded the lifetime of the colored form 3 and 3' in the micro- or nanosecond range.

Synthesis and evaluation of 17-aliphatic heterocycle-substituted steroidal inhibitors of 17alpha-hydroxylase/C17-20-lyase (P450 17).

In the search for potent inhibitors of P450 17, the key enzyme in androgen biosynthesis, a series of steroidal inhibitors were synthesized and tested toward rat and human P450 17. Small aliphatic heterocycles (aziridine, oxirane, thiirane, diaziridine, diazirine, azetidine) were introduced into the 17beta-position of anstrost-5-en-3beta-ol. After identifying that aziridine is the most suitable functional group to coordinate with the heme iron, modifications of the steroidal skeleton were performed for further optimization. A wide range of inhibitory potencies toward P450 17 were found for the 21 test compounds. The most potent inhibitors toward the human and rat enzyme were aziridine compounds 3 (IC(50) rat: 0.21 microM, K(i) = 3 nM; IC(50) human: 0.54 microM, K(i) = 8 nM), 5 (IC(50) rat: 0.43 microM, K(i) = 7 nM; IC(50) human: 0.29 microM, K(i) = 4 nM), and 8 (21R:21S = 1:1; IC(50) rat: 0.53 microM, K(i) = 9 nM; IC(50) human: 0.40 microM, K(i) = 6 nM) which were more potent than the reference ketoconazole (IC(50) rat: 67 microM; IC(50) human: 0.74 microM). The inhibitory potency depends markedly on the stereochemistry at C20 of the inhibitors. This effect is more pronounced for the rat enzyme. Tested for selectivity, the highly potent inhibitors show poor inhibitory activity toward P450 arom, P450 scc, P450 TxA(2), and 5alpha-reductase. Tested for in vivo activity, 3 and 8 (0.019 mmol/kg) decreased the plasma testosterone concentration in rats by 81% and 84% after 2 h.

The First Crystal Structure of a Germanium(II) Amide with a Germanium - Lithium Bond and Its Behavior Towards Oxygen and Water.

The Ge-Li bond in 1 reacts readily with water and oxygen to give 2 (Li/H exchange) and 3 (insertion), respectively. In both cases the partial charge and the oxidation state of the germanium atom changes. All compounds were characterized by X-ray crystallography.

Dinuclear and Tetranuclear Cages of Oxodiphenylantimony Phosphinates: Synthesis and Structures.

The novel dimeric compounds [Ph(2)Sb(O(2)PR(2))O](2).2CH(2)Cl(2) [R = cycl-C(6)H(11) (2) and cycl-C(8)H(15) (3)] have been synthesized by reacting diphenylantimony trichloride (1) with 3 mol equiv of silver acetate followed by 1 mol equiv of the phosphinic acid. By the same route under more stringent conditions to exclude moisture, the mixed phosphinate-acetate [Ph(2)Sb(O(2)P(C(6)H(11))(2))(O(2)CMe)](2)O (4) was isolated and characterized. Treatment of 2 with acetic acid/water affords the tetranuclear cage Ph(8)Sb(4)O(4)(OH)(2)(O(2)P(C(6)H(11))(2))(2).CH(3)COOH.CH(2)Cl(2) (5); it is possible to convert 5 to 2 by heating it with an excess of the phosphinic acid. Compounds 2, 3, and 5 have been characterized by X-ray structural analysis. All of them possess four membered Sb(2)O(2) rings with hexacoordinated antimony. In 5 the antimony atoms in the two Sb(2)O(2) rings are connected by oxo bridges on two sides to give an Sb(4)O(6) cage. These structures are correlated with those of known tin cages.