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Chapter 25 797
Copyright © 2017 Pearson Education, Inc.
25.
There are two 1,2-hydride shifts and two 1,2-methyl shifts. The last step is elimination of a proton.
HO
CH
3
CH
3
H
CH
3
CH
3
CH
3
H
3
C
H H
+
1,2-hydride
shift
HO
CH
3
CH
3
H
CH
3
CH
3
CH
3
H
3
C
H
+
1,2-hydride
shift
HO
CH
3
CH
3
H
CH
3
CH
3
CH
3
H
3
C
+
1,2-methyl
shift
HO
CH
3
H
CH
3
CH
3
CH
3
+
CH
3
H
3
C
1,2-methyl
shift
HO
CH
3
H
CH
3
CH
3
H
3
C
CH
3
CH
3
B
HO
CH
3
CH
3
CH
3
CH
3
H
3
C
CH
3
+
HB
+
protosterol cation
+
26.
A
B
-hydrogen
at C-5 means that the A and B rings are
cis
fused; an
A
-hydrogen
at C-5 means that they
are
trans
fused.
27.
Because the OH substituent is on the
same side
of the steroid ring system as the angular methyl groups, it
is a
B
-substituent
.
28.
CH
3
H
CH
3
H H
O
C
O