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Synthesis of Purine - Amino Acid Conjugates
Čapek, Petr ; Hocek, Michal (advisor) ; Kotora, Martin (referee) ; Dvořák, Dalimil (referee) ; Mazal, Ctibor (referee)
4. Conclusions A simple and efficient approach to the synthesis of (purin-6-yl)alanines based on Negishi cross-coupling reactions of 6-iodopurines and iodozinc- alanines applicable to the synthesis of both racemic and optically pure compounds was developed. Though analogous reactions were used before for the synthesis of some simple aryl- or hetarylaranines, this was the first successful use in the functionalization ofprotected nucleobases and nucleosides. A practical method for synthesis of enantiomerically pure (purin-6_ yl)phenylalanines by palladium catalyzeď, copper mediated Stille cross-coupling reactions ofprotected 4-(trimethylstanyl)phenylalanines and 6-iodopurines was developed. This method was used in the synthesis of series of (purin_6_ yl)phenylalanines (bases and nucleosides) varying in substitution in position 9 of purine scaffold and in absolute configuration on o-carbon ofphenylalanine. The shaughnessy method for the Suzuki cross-coupling reactions in aqueous media was further optimized and applied to the single-step synthesis of novel optically pure (adenin-8-yl)phenylalanines and (purine_6_yl)phenyl_ alanines. wide tolerance of this methodology towards variety of functionalities and its applicability to 1abile systems was demonstrated particularly by the very first examples of couplings...
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Measurement of \kur{in situ}Phasporus Availability in Acidified Soils using Iron-Infused Resin soils.
ČAPEK, Petr
A hybrid anion resin was tested for in situ phosphorus (P) availability measurement in soils of two stands recovering from acidification and having different P-sorption characteristics. The phosphate (P-PO4) sorption capacity of the resin (before saturation) was 48 mol g-1. Sorption and elution were tested under P-PO4 concentrations common in acidic soils (0 0.42 mmol l-1) either with or without the presence of sulfate (0.2 mmol l-1). The efficiency of P-PO4 sorption was independent of the sulfate and was 100 +/- 0.2% (n = 56, +/- SD). The P-PO4 recovery stabilized after six elution steps (each: 50 ml of 0.5 M sodium hydroxide, resin/solution 5:1). The efficiency of P-PO4 recovery was 80 +/- 7% and was used to evaluate field measurements. We determined the amount of P-PO4 in the field using resin bags in three consecutive years. The results indicate that bioavailable P is negatively related to the soil ability to retain P.
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Role fosforu v biologické aktivitě kryogenních půd
ČAPEK, Petr
The combined effect of temperature, moisture and phosphorus availability on soil organic matter mineralization in permafrost affected soils of northern circumpolar region was investigated. This study was a part of research activities of the European project CryoCARB and it was primarily focused on the cryoturbated organic horizons of permafrost affected soils. During this study, the temperature sensitivity of the organic matter mineralization and its relation to the soil moisture and phosphorus availability was investigated using series of incubation experiments and field measurements.
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Microbial biomass phosphorus measured by extraction-fumigation method
ČAPEK, Petr
The aim of this study was to assess posible sources of unacuracy in measurement of soil microbial phosphorus by extraction-fumigation method. The biggest one is the correction for sorption in two forest soils of watershed Plešné lake and Čertovo lake and one waterlodged soil. We also tried to assess the correction factor (Kp) for these soils, but we were unsuccesful. We would like to assess extractability of phosphorus sorbed during fumigation and assess Kp factor in future. Therefore we set up an appropriate methodology.
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\kur{In-situ} available phosphorus in forest soils of Bohemian forest lakes watersheds
ČAPEK, Petr
The aim of the study was to test ion exchange resin (IER) bag method for measurement of forest soil phosphorus availability. P-PO4 sorption and elution efficiencies of ion exchange resin AsenXnp (Purolite) were tested. The results showed nearly 100% efficiency of P-PO4 sorption. Average elution efficiency after repeated elution on a glass column was 87 % (each elution step 50 ml 2 % NaOH, 300 ml in total). The amount of available phosphorus was determined in-situ using IER bag method in the litter and organic soil layers of Plešné and Čertovo lakes watersheds. Amount of available phosphorus was 3.6 times greater in soils of Plešné watershed compared to Čertovo watershed.
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