Ergosta-5,7,9 ,22-tetraen

Artemisia annua Colletotrichum sp. 3P OH-ergosta-5-ene 3-oxo-ergosta-4,6,8(14),22-tetraene 67... 

Bond.— Side chain dehydrogenation is reviewed by Lederer. Unlike the dehydrogenations of the steroid nucleus, introduction of the Irons A -double bond of ergosterol and related steroids does not require the presence of a or A -double bond. However, the suggested formation of ergosta-5,7,22,24(28)-tetraen-3) -ol is supported by incorporation studies. The stereochemistry of this process is species-dependent. In protozoa Ochromonas tetrahymena) the (22R)- and (23S)-hydrogens of cholesterol are lost, i.e. the hydrogens at these positions derived from [2R- H,3R]- and [3R,5R-... 

Ergosta-5,7,22,24(28)-tetraen-3jS-ol has been synthesised from ergosterol by ozonolysis to the 22-aldehyde and construction of the appropriate side-chain using a Wittig reaction. During these reactions, the 5,7-diene system was protected as the Diels-Alder adduct (546) with 4-phenyl-l,2,4-triazolin-3,5-dione, from which the homoannular diene could be regenerated in 99 % yield by reduction with lithium aluminium hydride. 

VITAMIN D2 FROM ERGOSTEROL (9,10-Secoergosta-5,7,10(19),22-tetraen-3-ol,(3p)-from Ergosta-5,7,22-trien-3-ol,(3p)-)... 

Tancogne, J. Presence of ergosta, 6,8(14),22-tetraen-3-one and ergosterol in mold-infested tobacco Ann. Tabac 14 (1977) 197-204. 

Protection of the ring-B diene system in ergosterol acetate (390) as its adduct (391), followed by bromination of the C-22 double bond to (392) and dehydro-bromination with l,5-diazabicyclo[4,3,0]non-5-ene (DBN) in toluene, gave ergosta-5,7,22,24(28)-tetraen-3)8-ol acetate (393). 

As another example, consider ergosta-3,5,7,9-tetraene-3-acetate (I) ... 

Delseth C, Kashman Y, Djerassi C (1979) Ergosta-5,7,9(ll),22-tetraen-3P-ol and its 24 -ethyl homolog, two new marine sterols from the Red Sea sponge Biemna fortis. Helv Chim Acta 62 2037-2045... 

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