D. Complex Poly cyclic Compounds
155
ο
ο
ο
^
Me—C^^ÎF
\^ΞΥ^
I L
II
Me—C J!
NHII
NOH°
II °
I °
NOR
COMe
113
114
115
116
a: R = H
b: R = S0 2 Me
OH
FOF
Ρ
Ρ
>^
XH\
/
H\
Cl
I
J
If
H a O a
I
|^
\""r\ NaBH 4 .
CH 2 S0 3 H
Ι
I
JJ OH"
I
I
V°
I Ο
I -H
Ac O
Ac Ο
COMe
117
118
119
Φ
/ά>Μ» « X L , / Λ
>// 0 HOA C>
"Γ
4 a [
J
=
Ν \
\U^HO\
AcO* ^V^^F^OH
AcOΤ
9
ΝΗΪ
8
AU
Ac OR
Ac OAc
U r
t
120
121
a: R = Η
b: R = Ac
SCHEME 4.5
Goto's successful completion of his total synthesis of tetrodotoxin has
now been reported (Goto, 1971).
It may be recalled that a great variety of drastic degradations of tetrodotoxin (111) led to a number of closely related quinazoline derivatives 108.
Once the complete structure of tetrodotoxin was known it became evident
that the molecule indeed contained a hydroquinazoline skeleton possessing a
carbon substituent in one of the angular positions. Keana and co-workers
(1969) in their first approach toward a total synthesis of tetrodotoxin achieved
the construction of a suitably substituted hydroquinazoline by way of a
novel Diels-Alder reaction. The heterocyclic dienophile 124 resulted from