A Stereospecific Total Synthesis of Chasmanine

Synthesis of Cardiopetaline via a Wagner–Meerwein Rearrangement without Preactivation of the Pivotal Hydroxy Group

“…Activation of the diol moiety in 10 with thionyl chloride to form a cyclic sulfite, or with trimethyl orthoformate to form a cyclic orthoester, did not induce the desired rearrangement. While treatment of 10 with dilute sulfuric acid at 110 °C caused only cleavage of the TBS ether to give the corresponding triol, the same reaction at 140 °C produced a trace amount of cardiopetaline (6). After screening a variety of Brønsted acids, we found that a combination of p-toluenesulfonic acid and acetic acid efficiently accelerated the rearrangement reaction.…”

“…To our delight, by employing pivalic acid instead of acetic acid, the rearrangement proceeded smoothly to give a mixture of pivalates 13 (Scheme 3), 18,19 which was hydrolyzed under basic conditions to afford cardiopetaline ( 6) in 84% yield. 20 In conclusion, we have achieved a simple conversion of the denudatine skeleton into the aconitine skeleton via a Wagner− Meerwein rearrangement, leading to a synthesis of cardiopetaline (6). The rearrangement could be accomplished by heating a diol with p-toluenesulfonic acid in pivalic acid, without preactivation of the hydroxy group.…”

“…7 Sarpong and coworkers recently reported concise total syntheses of weisaconitine D (5) and liljestrandinine using the rearrangement reactions of triflates. 8 We have also achieved the synthesis of cardiopetaline (6) via the rearrangement of a sulfonyloxirane. 9,10 For the Wagner−Meerwein rearrangement, stereoselective installation of a leaving group in the substrate is often carried out via activation of a hydroxy group as a sulfonate.…”

Enzymology and Physiology of Reticulocyte Lipoxygenase: Comparison with Other Lipoxygenases

“…Earlier studies have revealed that the respirationinhibitory activity of the lipoxygenase is absent both in bone marrow and in mature erythrocytes qf nonanemic rabbits. The activity starts to increase on the third day to reach peak levels on the sixth day of an experimental anemia provoked by strong daily bleeding (14,179). During this period the share of reticulocytes increases from Percentage of reticulocytes and lipoxygenase activity in the course of an 1-3% to approximately 40% of the total red cells.…”

“…During this period the share of reticulocytes increases from Percentage of reticulocytes and lipoxygenase activity in the course of an 1-3% to approximately 40% of the total red cells. With cell populations obtained by buoyant density centrifugation it has been shown that very young reticulocytes of low density and high RNA content exhibit only little or no lipoxygenase activity (179). A sharp maximum of lipoxygenase is found with more mature reticulocytes followed by a steep decline during the transition to the normocyte.…”