Estimation of the Water Resources Potential in the Island System of the Aegean Archipelago, Greece
摘要:
The present paper tries to estimate the surface water resources potential in some of the major Aegean islands in an effort to provide a means for the continuous development of the region, and, by extension, for similar areas around the world The islands have to confront the challenge of surviving in a semiarid environment under the constraints of uneven water resources distribution both in space and time. In addition to these, tourism development, industrialization and highly water consumptive life styles have exacerbated perennial problems in water resources and water resources management. The framework of the present effort has a two-prong emphasis. In the first part, a simulation model is presented, which tries to estimate the potential surface runoff under physical, structural organizational, and institutional constraints. The methodology and the premises' of the simulation process are delineated In the second part, the results of the model application in distinct cases are demarcated. The final product, namely the model and the resulting runoff coefficients, are presented in the form of a standard, which may provide practitioners in the field as well as decisionmakers the means for an initial reference in pertinent developmental efforts. Finally, the conclusions and recommendations raise the question of ecosystem resilience and point towards the urgent and continuous need for the application of integrated-water resources management principles.
Reaction of nitro-alkenes with iodotrimethylsilane: a new method for the conversion of vinyl nitrosteroids to ketosteroids
作者:Gireesh M. Singhal、Nalin B. Das、Ram P. Sharma
DOI:10.1039/c39890001470
日期:——
Iodotrimethylsilane generated in situ from chlorotrimethylsilane and sodium iodide effects the reduction of nitro-alkenes (1a–e) and (5) at –5 to 0 °C to furnish the ketones (2a–e) and (6) respectively as the major products.
Synthesis of 5.ALPHA.-cholestan-6-one derivatives with some substituents at the C-1, C-2, or C-3 position.
作者:SUGURU TAKATSUTO、NOBUO IKEKAWA
DOI:10.1248/cpb.35.986
日期:——
In order to investigate the regioselectivity of Baeyer-Villiger oxidation, thirty 5α-cholestan-6- one derivatives with various substituents (methyl, hydrogen, acetoxymethyl, methoxy, acetyloxy, benzoyloxy, trifluoroacetyloxy, p-toluenesulfonyloxy) at the C-1, C-2, or C-3 position were synthesized from cholesterol. The 6-oxo functional group of 5α-cholestan-6-one derivatives was introduced via hydroboration. The 3β-derivatives were readily obtained by using the native 3β- hydroxyl group of cholesterol. The 3α-isomers were obtained by inversion of the configuration of the 3β-tosylate 24 with tetra-n-butylammonium acetate in refluxing 2-butanone. The 2β-isomers were derived from the 2-ene 43 by bromohydrination, LiAlH4 reduction, and esterification. The 2β- to 2α-hydroxyl group inversion was achieved by Birch reduction of the 2-oxo steroid 51. The 1α-derivatives were derived from the known 6β-acetoxy- 1 α-hydroxy-5α-cholest-2-ene (57).
Remote substituent effect on the regioselectivity in the baeyer-villiger oxidation of 5α-cholestan-6-one derivatives
作者:Suguru Takatsuto、Nobuo Ikekawa
DOI:10.1016/s0040-4039(00)81564-6
日期:——
The regioselectivity in the Baeyer-Villiger oxidation of 5α-cholestan-6-one derivatives was markedly affected by the substituents at C-1, 2 or 3 position which were located at γ or δ position from the reaction center c-6.
Aspects of the Reduction of Double Bonds Using Cob (I)alamin as Catalys
作者:Albert Fischli
DOI:10.1002/hlca.19820650839
日期:1982.12.15
The olefinic system in 3β-methoxy-4-cholesten-6 a-ol (2) is reduced using cob (I)alamin (1(I); see Scheme 1) as catalyst, aqueous acetic acid as solvent and metallic zinc as electron source (cf. Schemes 2 and 3). Experimental evidence for an attack of 1(I) on both faces of the double bond is presented. By the same catalyst (1 R)-10, 10-dimethyl-2-pinene- 10-carbonitrile (9) is first transformed to
and 4n, and showed an additive or synergistic effect with vancomycin or oxacillin. On the other hand, the derivative 4f, which carries a spermine moiety like that of the natural trodusquemine molecule, was found to be the most active derivative against all the resistant Gram-negative bacteria tested, with an MIC value of 16 µg/mL. Our results suggest that 6-polyaminosteroid analogues of squalamine are