114
H. Zhu et al.
HN
O
O
OH
O
344 (aspochalasin B)
O
HO
OH
OH
HO
1) CSA, toluene, 80°C
2) Ac 2 O, DMAP, DCM
30% (5:1)
AcO
OAc
AcO
O
HN
O
O
OAc
O
AcO
OAc
OAc
O
HN
O
O
OH
O
O
HO
OH
O
HO
O
OH
HO
O
HN
O
O
OH
O
O
OH
HO
O
HN
O
O
OH
O
448 (asperchalasine B)
451 (asperchalasine E)
O
OH
HO
O
HN
O
O
OH
O
451 (asperchalasine E)
HO
O
OH
O
HN
O
O
OH
O
350 (asperchalasine D)
BnO
OBn
OBn
O
HN
O
O
OH
O
BnO
OBn
BnO
O
HN
O
O
OH
O
CSA, toluene, 60°C
63% (10:1)
1) CSA, toluene, 60°C
2) Raney Ni, H 2 , EtOH
57% (3:2)
O
HO
OBn
O
BnO
O
HO
OBn
OBn
BnO
CSA, toluene, 60°C
80% (3:2)
Raney Ni
H2, EtOH
455 (asperchalasine A)
HO
OH
HO
O
HN
O
O
OH
O
Air
O
O
HO
O
HN
O
O
OH
O
[5+2]
aspochalasin B
I13
I14
I15
I16
I17
I18
I19
I20
I21
I22
O
O
HO
HN
O
OH
O
NH
O
O
O
HO
O
57% from I19
O
Scheme 16 Total syntheses of asperchalasines A–E