PubMed · 4466951
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N N Savitskiĭ. 1974. [Reasons for prophylactic digitalization].. https://pubmed.ncbi.nlm.nih.gov/4466951/
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Two methods have been developed for efficient conversion of pregna-14,16-dien-20-ones into 14 beta-hydroxyandrost-15-en-17-ones. One procedure consists of treatment of the ring-D dienone successively with sodium borohydride and singlet oxygen. The reaction is illustrated by the conversion of pregna-14,16-dien-20-one 1 into 14 beta-hydroxyandrost-15-en-17-one 3, via the corresponding allylic alcohol 2. Although this two-step procedure is simple, it provides 3 in relatively low yield, accompanied by a smaller amount of the isomeric 14 alpha-hydroxyandrost-15-en-17-one 6. An alternative one-step conversion is achieved by treatment of dienone 1 with a peroxyacid in the presence of a strong protic acid. This process is illustrated by the two-step conversion of dienone 1 into hydroxy ketone 11 in 51% overall yield (Scheme 5) and by the analogous conversion of dienone 13 into hydroxy ketone 24 in 61% overall yield (Scheme 11).
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The positive inotropic and electrophysiological effects of cardiac glycosides on cardiac muscle are mediated through inhibition of Na+/K+ ATPase by binding to a specific extracytoplasmic site of the a-subunit of this enzyme. The inhibition of Na+/K+ ATPase affects ionic flux and produces direct local effects on cardiac contractility, electrical excitability and conduction, but also profound systemic effects mainly as a result of haemodynamic changes. These effects are responsible for beneficial therapeutic as well as toxic effects. Inhibition of Na+/K+ ATPase results in potentiation of K+ loss from cells and Na+ entry into cells, so consequently affects action potential generation and propagation. This also underlines the potentiation of certain effects of cardiac glycosides by hypokalemia and hypomagnesaemia, and the effects of changes in calcium homeostasis on the cardiac glycoside pharmacodynamics. Furthermore, inhibition of Na+/Ca++ exchange enhances Ca++ mobilization and promotes contractility. These effects (locally and systemically) differ greatly, depending on the haemodynamic status and myocardial oxygen supply. Cardiac glycosides have less affinity for Na+/K+ ATPases at other sites (e.g. skeletal muscle), but some extracardiac effects (vascular effects, effects on colour vision, CNS and autonomic effects, renal effects) may be related to Na+/K+ ATPase inhibition.