| Summary: | 碩士 === 國立臺灣大學 === 藥學研究所 === 84 === The Mycobacterium sp.(NRRL B-3805) is known for its capability
to cleave the 17-alkyl side chain of several sterols such as
choles- terol,sitosterol,stigmasterol,and campesterol with
formation of 17-keto steroids.In order to find out that whether
this microorg- anism is capable of cleaving the sapogenin-type
side chain,sarsa- sapogenin,dihydrosarsasapogenin and
kryptogenin were incubated with this microorganism.When
incubated with Mycobacterium sp.(NR- RL B-3805),the
sarsasapogenin kept the spirostane structure inta- ct as
expected,the only change is oxidation of the 3β-hydroxyl group
to carbonyl and introduction of a Δ4 double bond.This sa-
rsasapog-4-en-3-one is the major product and isolated in 62%
yie- ld.Dihydrosarsasapogenin was obtained from sarsasapogenin
by rea- cting with lithium aluminum hydride and aluminum
chloride. After incubation, we obtained 6 products (compounds
4-9).Compounds 4-6 were formed by the cleavage of the bond
between C-23 and C-25, then the C-24 acid were methylated to
form methyl ester.The most special is that the A,B rings of 5
and 6 are trans-juction inst- ead of cis-juction.It could not
be explained by the known mecha- nism.Compound 8 and 9 were
formed by breaking the bonding of C-22 and C-23,and were the
same as the microbial transformation prod- ucts of lanosterol
derivatives.Compound 7 was the only 19 carbons steroid,but the
same as 8 and 9,having a hydroxyl group at C-12. Kryptogenin is
devoid of rings E and F,the ring system in the sp- irostane,
and has keto functions at C-16 and C-22.We obtained 4 products
(compounds 11-14) after the incubation of kryptogenin with
Mycobacterium sp.(NRRL B-3805).Compound 11 is the same as
kryptogenin except the formation of 4-en-3-one.Compound 12 was
obtained by the cleavage of the bond between C-24 and C-25,and
formed C-24 alcohol.13 and 14 was supposed that the bond
between C-25 and C-26 was broken and formed C-25 alcohol or
C-25 ketone.
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