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47 IChO 2015 Baku – Azerbaijan Soluzioni preliminari dei problemi preparatori 1 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
O H BnO
OH O
H OH
BnO
O TsOH O
benzene ∆ ICl A
piridina OH
O H
BnO I
O H
BnO I
OBn
O OH
BnO I
OBn BnBr
B
NaClO2
C
K2CO3 NaH2PO4
A
D
EDC DMAP
O O
BnO I
O
O O
OBn O
O BnO
OBn O H
OBn
O
O O BnO
O H BnO
E
1) Pd(OAc)2 AcONa PPh3
2) H3O+
F G
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47 IChO 2015 Baku – Azerbaijan Soluzioni preliminari dei problemi preparatori 2 O
O
O OH
O H
OH
O O BnO
OBn O H
OBn
nigricanin H2 ,Pd/C
CH3OH
F
OH
O H
BnO I
O H
BnO I
O O
O OH
BnO I
O O
MOMCl
B
NaClO2
H
NR3 NaH2PO4
A
I
EDC DMAP
O O
BnO I
O
O O
OBn O
O
O O O O
H
BnO
OBn
J
1) Pd(OAc)2 AcONa, PPh3
2) H3O+
H2 ,Pd/C CH3OH
K
O O
O OH
O H
OH
nigricanin
Soluzione proposta da
Mauro Tonellato - ITI Marconi - Padova
