Solanum alkaloids, 121. Partial Synthesis of the Steroid Alkaloids Teinemine, 22‐Isoteinemine, Etioline, and 25‐Isoetioline

Abstract

The rare 16α‐hydroxylated steroid alkaloids teinemine [(22S,25S)‐22,26‐epiminocholest‐5‐ene‐3β,16α‐diol, 8], 22‐isoteinemine [(22R,25S)‐22,26‐epiminocholest‐5‐ene‐3β,16α‐diol, 10], etioline [(25S)‐22,26‐epiminocholesta‐5,22(N)‐diene‐3β,16α‐diol, 12], and 25‐isoetioline [(25R)‐22,26‐epiminocholesta‐5,22(N)‐diene‐3β,16α‐diol, 21] are synthesized from the abundant spirosolane alkaloids tomatid‐5‐en‐3β‐ol [(25S)‐22βN‐spirosol‐5‐en‐3β‐ol, 1] and solasodine [(25R)‐22αN‐spirosol‐5‐en‐3β‐ol, 15], respectively. The crucial stages of these syntheses are the conversions of 1 or 15 into the N‐protected (22S,25S)‐, (22R,25S)‐, and (22S,25R)‐22,26‐epimino‐3β‐hydroxycholest‐5‐en‐16‐ones 6, 7, and 18 as well as their reductions with sodium/ 2‐propanol to the 16α‐hydroxy compounds teinemine (8), 22‐isoteinemine (10), and (22S,25R)‐22,26‐epiminocholest‐5‐ene‐3β,16α‐diol (19), respectively. By treatment with sodium methanolate the N‐chloro derivatives 9 and 11 of 8 and 10 afford etioline (12). In an analogous manner, the N‐chloro derivative 20 of 19 is converted into 25‐isoetioline (21).

A Novel Antiprotozoal Aminosteroid from Saracha punctata

“…Detailed analysis of ROE and inter-proton coupling constants in the piperidine ring of 1 allowed the determination of the relative configurations of C-22 and C-25 but not their absolute configurations. The determination of the C-22 and C-25 configurations in 22,26-epiminosteroids has been an object of debate and controversy settled by a still unpublished X-ray crystallographic study and a partial synthesis. , Owing to the equatorial nature of CH 3 -27 (δ C 19 ppm vs 16 ppm), compound 1 does not have the side chain of desacetylmuldamine (or teinemine), nor does it have the configuration of isoteinemine.…”

“…The determination of the C-22 and C-25 configurations in 22,26-epiminosteroids has been an object of debate and controversy settled by a still unpublished X-ray crystallographic study and a partial synthesis. 11,14 Owing to the equatorial nature of CH 3 -27 (δ C 19 ppm vs 16 ppm), compound 1 does not have the side chain of desacetylmuldamine (or teinemine), nor does it have the configuration of isoteinemine.…”