Biomedical Engineering Reference
In-Depth Information
1. Oxone
2. KOH
3. TMSOTf
MeOH
OR
DDQ
CH
2
Cl
2
/H
2
O
reflux
OMe
S
O
O
HO
O
S
O
S
BnO
OH
89-92%
O
HO
S
OR
MPMO
420
421
422
1. Ra-Ni
2. OsO
4
3. TMSOTf/MeOH
a. MPM removal
b. Oxidation
e. Second cyclisation
O
OH
c. Isopropylidene
groupe hydrolysis
d. First cyclisation
S
O
HO
OMe
O
HO
O
H
S
O
RO
S
BnO
OH
OR
S
O
423
424
425
SCHEME 9.74
Synthesis of
L
-sugar derivatives
422
and
425
.
) has recently been isolated from a Papua New Guinea col-
lection of
L. bouillonii
and identified as a new potent molluscicidal agent [164]. These
compounds are of great interest for controlling schistosomiasis carrying snails of the
genus
Biomphalaria
by intercepting the aquatic snail vector [165]. Hong and Kim
used a domino oxidation/oxa-Michael reaction to prepare 2,6-
cis
-tetrahydropyran
methyl ester
Cyanolide A (
428
427
as part of the skeleton of cyanolide A (
428
) starting from the chiral
allylic alcohol
(Scheme 9.75) [166].
The recently isolated sesquiterpenoid natural product (
426
),
bearing a dioxa[5.5.5.6]fenestrane ring system, has been shown to exhibit specific
activity against the armyworm
Spodoptera frugiperda
that is responsible for the
destruction of various crops including grain [167]. In the recently published synthesis
of
)-penifulvin A (
432
432
, Mulzer and Gaich [168] prepared the intermediate
430
from
429
via a
suprafacially selective
meta
-photocyclization [169]. Hence, treatment of
430
with
431
ozone initiated a domino oxidation and cyclization sequence to afford
, which was
432
eventually converted to the natural product
(Scheme 9.76).
MnO
2
, CH
2
Cl
2
, rt, 4 h
Dimethyl triazolium iodide
DBU, MnO
2
, MeOH, rt, 12 h
S
S
HO
MeO
2
C
S
S
HO
O
88%
PMBO
PMBO
426
427
OMe
steps
O
OMe
O
O
O
O
MeO
OMe
O
O
O
MeO
O
O
OMe
Cyanolide A
428
SCHEME 9.75
Synthesis of cyanolide A
428
by Hong and coworkers.
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