Chemistry Reference
In-Depth Information
1) PivCl, pyridine,
CHCl
3
(63%)
2) TMSN
3
,SnCl
4
,
CH
2
Cl
2
(93%)
H
2
, Raney-Ni,
MeOH (87%)
HO
PivO
OH
OPiv
PivO
OPiv
O
O
O
OH
HO
N
3
PivO
NH
2
PivO
OH
OPiv
OPiv
66
67
D-Galactose
OSiMe
3
PivO
OPiv
O
MeO
OHC
N
PivO
67
ZnCl
2
•Et
2
O,
THF, -20 °C
OPiv
pentane,
MS4A
68
(68%)
1) NaIO
4
,K
2
OsO
4
,
aq. dioxane (75%)
2) NaOH,
dibenzo-18-cr-6,
benzene (81%)
Me
Me
PrMgCl,
CuCl, BF
3
•Et
2
O,
THF, -78 °C
PivO
OPiv
O
O
O
O
N
N
N
Xc
PivO
Xc
(81%)
OPiv
Xc
(
dr
>40:1)
71
69
70
(
dr
>10:1)
1) 1,2-ethane-
dithiol,BF
3
Et
2
O
2) H
2
, Raney-Ni
3) HCl
1) Me
2
CuLi
TMSCl, THF,
-78 °C
2) TBAF
(81%)
Me
Me
Me
O
1) HCl, aq. MeOH
2) CbzCl, NaHCO
3
H
H
O
71
N
H
Xc
(93%)
Me
N
Me
N
Me
H
HCl
Cbz
(37%)
73
74
4a-
trans-epi
-
pumiliotoxin C
72
(
dr
>15:1)
Scheme 2.13
Total synthesis of 4a-
trans
epi-pumiliotoxin (
74
) from per-
O
-pivaloyl-
β
-d-
galactosylamine (
67
).
-glycosylamine
67.
As a representative
example of stereoselective carbon-carbon bond-forming reactions using
67,
the Kunz group developed the tandem Mannich/1,4-addition reaction of various
glycosylimines prepared from
67.
The products of this reaction sequence are
starting materials for the synthesis of structurally simple piperidine alkaloids
[25]. Later, the Kunz group has extended this strategy using
67
as a chiral platform
for the synthesis of functionalized decahydroquinoline-type alkaloids. As shown
in Scheme 2.13,
Hydrogenation of
66
provided the
β
-d-galactosylimine
68,
prepared from
67
and 5-hexenal, was
treated with the Danishefsky-Kitahara diene in the presence of ZnCl
2
·Et
2
O
to provide in excellent diastereoselectivity (dr
β
40 : 1) galactopyranosyl 5,6-
dehydropiperidin-4-one
69,
which possesses a 4-pentenyl substituent at C2 with
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