No abstract

A B S T R A C T After intravenous administration of radiolabeled 1,25-dihydroxyvitamnin D3 to rats, -25% of the administered radioactivity appeared in the bile within 24 h. Instillation of the biliary radioactivity into the duodena of other rats was followed by recovery of 15% of the radioactivity in newly secreted bile within 24 h. The process by which products of 1,25-dihydroxyvitamin D3 were excreted in bile was not saturable in the dose range tested (0.275-650 ng). The metabolites of 1,25-dihydroxyvitamin D3 present in bile were found to be much more polar than 1,25-dihydroxyvitamin D3 and were resolved into three fractions on high performanice liquid chromatography. 60% of the radioactivity present in bile was retained selectively by DEAE-cellulose; the radioactive material could be eluted from the gel at a low pH or at high salt concentrations. When bile containing the radiolabeled metabolites was incubated at 37°C and pH 5 with f3-glucuronidase, there was an increase in the amount of radioactivity comigrating with 1,25-dihydroxyvitamin D3. Treatment of the products of radiolabeled 1,25-dihydroxyvitamin D3 in bile with diazomethane, an agent which converts acids into methyl esters, transformed one of the metabolites into a less polar compound. These results demonstrate that there is a quantitatively important enterohepatic circulation of the products of 1,25-dihydroxyvitamin D3 in the rat.

The Bischler‐Napieralski dihydroisoquinoline synthesis was proven to occur via imidoyl chlorides and the corresponding nitrilium salt. The two‐step process required much milder conditions (20°–50°) compared to drastic classical conditions of refluxing at 100°–200°. The Bischler‐Napieralski reaction is shown to share a common intermediate with two other well‐known reactions: the von Braun and the Ritter reactions.

A B S T R A C T Evidence has beenThese results suggest the existence of a mechanism for reutilization of the biliary products of vitamin D3.

No abstract