RESUMEN
The first and asymmetric total synthesis of 4ß-acetoxyprobotryane-9ß,15α-diol, containing a rare and highly strained trans-fused bicyclo[3.3.0]octane ring system, has been achieved. The synthetically challenging [6-5-5] tricyclic ring system in the final product was efficiently and diastereoselectively synthesized via an asymmetric rhodium-catalyzed [4 + 2] cycloaddition reaction, followed by a unique benzilic acid type rearrangement under very mild conditions. The seven contiguous stereocenters were installed efficiently and diastereoselectively.
RESUMEN
The first and asymmetric total synthesis of bioactive bufospirostenin A, an unusual spirostanol with rearranged A/B rings, was accomplished. The synthetically challenging [5-7-6-5] tetracyclic ring system, found in bufospirostenin A and some other natural products, was efficiently constructed by the unique intramolecular rhodium-catalyzed Pauson-Khand reaction of an alkoxyallene-yne. The 11 stereocenters in the final product, including the 10 contiguous stereocenters, were installed diastereoselectively.
RESUMEN
CONTEXT: A novel N-succinyl chitosan/alginate hydrogel bead was prepared by the ionic gelation method for controlled delivery of nifedipine (NF). OBJECTIVE: The delivery behavior of NF from the hydrogel bead was studied in rabbit body. MATERIALS AND METHODS: Nitrendipine was used as the internal standard and the concentration of NF in serum was determined by reversed-phase high-performance liquid chromatography. RESULTS: The assay was linear from 5 to 755 ng/mL. The limit of quantitation for NF was 5 ng/mL in serum, and the recovery was greater than 90%. The method was used to determine the concentration-time profiles of NF in the serum. The pharmacokinetic parameters were calculated by Drug and Statistics (ver 1.0) program. The mean Cmax was 320.2 ± 71.3 µg/L, the mean Tmax was 3.2 ± 0.5 hours, the mean t1/2 was 6.60 ± 2.17 hours, the mean AUC0-24 was 2.03 ± 0.25 mg h/L, the mean AUC0-∞ was 2.50 ± 0.36 mg h/L, the mean MRT0-24 was 8.57 ± 0.19 hours, and the mean MRT0-∞ was 15.2 ± 1.8 hours. DISCUSSION AND CONCLUSION: The pharmacokinetic characteristics were found by a two-compartment model following the oral administration of NF-loaded N-succinyl chitosan/alginate hydrogel beads in rabbits.
