A reação de tert-butil 2-(3-cloro-1,4-dioxo-1,4-di-hidronaftalen-2-ilamino)etilcarbamato com CF3COOH/CH2Cl2 fornece 5-cloro-3,4-di-hidrobenzo[f]quinoxalin-6(2H)-ona. Este composto sofre desidrogenação promovida por ácido na presença de água para dar a 5-clorobenzo[f]quinoxalin-6-ol, inédita. A estrutura molecular no estado sólido, determinada por um estudo de difração de raios X (XRD), e os dados em solução confirmam que a benzoquinoxalina existe na forma do tautômero enol-imina, tanto no estado sólido, quanto em solução, diferentemente de 5-cloro-3,4-di-hidrobenzo[f]quinoxalin-6(2H)-ona que exibe o arranjo ceto-amino. Cálculos de teoria do funcional da densidade (DFT) confirmam a preferência da benzoquinoxalina e dos compostos análogos contendo grupos H ou CH3 no lugar do Cl pela forma enol-imina. Sugere-se que a preferência da benzoquinoxalina pela estrutura enol-imina se deva ao maior caráter aromático desta estrutura em comparação com a forma ceto-amina. Os cálculos DFT dos dois tautômeros das benzo[a]fenazin-5(7H)-onas análogas às benzo[f]quinoxalin-6(4H)-onas indicaram que as estabilidades relativas são dominadas por efeitos de solvatação, no primeiro caso, e pelo grau de aromaticidade no segundo.

The reaction of tert-butyl 2-(3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) ethylcarbamate with CF3COOH/CH2Cl2 yields 5-chloro-3,4-dihydrobenzo[f]quinoxalin6(2H)-one which undergoes acid-promoted dehydrogenation in the presence of water to give novel 5-chlorobenzo[f]quinoxalin-6-ol. The molecular structure of 5-chlorobenzo[f]quinoxalin6-ol in the solid state, determined by an X-ray diffraction (XRD) study, and the solution data confirm that it exists as the enol-imine tautomer, both in the solid state and in solution, differently from 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one, which exhibits the keto-amine arrangement. Density functional theory (DFT) calculations confirmed the preference of 5-chlorobenzo[f]quinoxalin-6-ol and of the derivatives containing H and CH3 groups in place of the Cl atom for the enol-imine tautomer. It is suggested that the enol-imine structure is preferred for 5-chlorobenzo[f]quinoxalin-6-ol as a consequence of the higher aromatic character of this structure in comparison with the keto-amine form. DFT calculations carried out on the two tautomers of the benzo[a]phenazin-5(7H)-ones analogous to the benzo[f]quinoxalin-6(4H)-ones showed that the relative stabilities are dominated by solvation effects in the first case and the degree of aromaticity, in the latter.

The growth and the quantity and quality of carotenes produced by two Chilean strains of D. salina (CONC-001 and CONC-007), grown in two different media (PES and SM) were analyzed. No important differences were found between the two media either in the growth or in the carotenogenesis suggesting that the low-cost media (SM) would be appropriate for large scale culture of D. salina. The strain CONC-007 displayed the lower growth rate, but the highest productivity of carotenoid per cell and the highest 9-cis <FONT FACE=Symbol>b</FONT>-carotene content whereas the strain CONC-001 exhibited the highest growth rate but a lower accumulation of carotenoid per cell and a low 9-cis <FONT FACE=Symbol>b</FONT>-carotene content. The Chilean strains were both more carotenogenic than the reference strain Dunaliella bardawil

Se analizó el crecimiento así como la cantidad y calidad de los carotenos producidos por dos cepas chilenas de D. salina (CONC-001 y CONC-007) cultivadas en dos medios de distinta formulación (PES y MS). La composición del medio de cultivo no afectó el crecimiento ni la carotenogénesis de las cepas analizadas, sugiriendo que el medio de bajo costo (MS) podría ser apropiado para el cultivo de D. salina a mayor escala. La cepa CONC-007 presentó la menor tasa de crecimiento pero la mayor productividad de carotenoides por célula así como el mayor contenido de 9-cis <FONT FACE=Symbol>b</FONT>-caroteno, el cual corresponde al isómero de mayor interés comercial. Por otro lado, la cepa CONC-001 mostró la mayor tasa de crecimiento pero una menor acumulación de carotenoides por célula y un bajo contenido de 9-cis <FONT FACE=Symbol>b</FONT>-caroteno. Ambas cepas chilenas resultaron ser más carotenogénicas que la cepa de referencia Dunaliella bardawil