Problema 19 Pyrrolizidine alkaloids Very recently, the first total

Problema 19 Pyrrolizidine alkaloids Very recently, the first total

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Problema 19
Pyrrolizidine alkaloids
Very recently, the first total synthesis of nigricanin, one of the ellagic acid congeners, was described.
Decipher this scheme. Write down the structural formulae of compounds A–K accounting for the facts
that F and G are isomers; molecular formulae of D and E are C21H17IO4 and C37H31IO7, respectively.
Soluzione:
OH
HO
OH
OH
BnO
BnO
H
O
ICl
piridina
TsOH
benzene
∆
O
O
A
OBn
OH
BnO
I
BnO
BnBr
H
OBn
I
K2CO3
I
NaH2PO4
H
O
BnO
NaClO2
OH
O
B
EDC
DMAP
O
C
O
A
D
O
O
O
H
1) Pd(OAc)2
AcONa
BnO
PPh3
O
BnO
I
2) H3O
O
OBn
O
E
47 IChO 2015
Baku – Azerbaijan
BnO
OBn
O
OBn
O
H
+
O
O
BnO
O
F
G
Soluzioni preliminari dei problemi preparatori
1
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OH
O
H
O
OBn
H2 , Pd/C
BnO
OBn
HO
OH
CH3OH
O
O
O
O
nigricanin
F
O
O
OH
BnO
O
MOMCl BnO
I
H
O
I
NR3
NaClO2
H
O
BnO
I
NaH2PO4
OH
O
B
O
EDC
DMAP
O
H
O
A
I
O
O
O
H
O
1) Pd(OAc)2
AcONa, PPh3
I
BnO
2) H3O
O
O
BnO
OBn
+
O
H2 , Pd/C
CH3OH
OBn
O
O
J
K
OH
O
HO
OH
O
O
nigricanin
Soluzione proposta da
Mauro Tonellato - ITI Marconi - Padova
47 IChO 2015
Baku – Azerbaijan
Soluzioni preliminari dei problemi preparatori
2