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TBDPSO
TBDPSO
OH
O
O
O
57
58
OBn
TBSO
OHC
O
O
59
Br
OMe
Br
O
O
OMe
61
C
11
H
23
O
O
OMe
C
11
H
23
OMe
60
Ph
N
OTBS
O
O
O
O
I
BnO
BnO
O
O
O
63
62
64
OH
OH
O
C
12
H
25
O
O
OH
HO
Muricatetrocin C
Scheme 10-13. Total synthesis of muricatetrocin C by Dixon et al.
with L-selectride. The intermediate 61 was given after hydroxyl group protection.
Sonogashira coupling between 61 and 64, followed by selective hydrogenation and
deprotections, finally afforded muricatetrocin C.
Sharpless dihydroxylation, Co(II)-catalyzed oxidative trans-THF ring formation
served as the key steps in Wang et al.'s route to gigantetrocin A,
41
which generated
the THF-containing aldehyde 68 (Scheme 10-14). On the other hand, the ester 69
was prepared from L-glutamic acid. This ester was converted into the phosphorium
salt 70 after the lactone unit was introduced. The molecular skeleton was estab-
lished by Wittig reaction between 68 and 70, although the chemical yield was
less satisfactory. The total synthesis of gigantetrocin A was finally completed after
several
treatments,
including b-elimination
and
deprotection
of
the
hydroxyl
groups.
Although the absolute configurations remained unknown, the relative configura-
tion of the THF region of mosin B was known as erythro-trans-threo. In the synth-
esis published by Tanaka et al. (Scheme 10-15),
42,43
desymmetry of meso-
cyclohexene-4,5-diol was achieved by mono-benzyl etherification, which gave 71
enantioselectively. The olefin 71 was then converted into allylic alcohol 73 by sev-
eral steps including oxidative cleavage of the double bond and the Wittig reaction.
Iodoetherification and base treatment furnished the trans-THF fragment 74 with
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