Proof of Structure For 24β-Methylcholesterol in the Alga Coccomyxa elongata by ¹H- and ¹³C-nmr and Mass Spectroscopy

Abstract

The green alga Coccomyxa elongnta belonging to the order Chlorosphaerales (in the older literature Tetrasporales or Yolvocales) is known to contain a sterol mixture. An examination of the component in the largest amount by 1and 13C-nmr spectroscopy together witli mass spectral data rigorously proved it to be 243-methylcholesterol. In addition, our information indicated stereochemical purity. This alga, therefore, corresponds to the other green alga species investigated in that the 24-alkylsterols present have the 243-configuration.The chiral centers in sterols can be divided into those which are invariant and those which differ depending on the living systems in which they occur.Among the AYsterols, which appear to comprise the most common type, all of the chiral centers at ring junctions fall into the invariant category so far as is known (1, 2). Two centers in the side chain also appear to be invariant. Timare at C-20 and the point (C-17) where the side chain meets the tetracyclic system (1-4). Thus, it is possible to describe all naturally occurring A* *5 *7-sterols as having the stereochemistry of cholesterol at C-8, C-9. C-10, C-13, C-14. C-17, and C-20. However, when C-24 is rendered chiral by the introduction of an alkyl group, variance at this position occurs.