14
1. Isoprenoids
conversion of the three phenols to the corresponding aplysin derivatives. By
means of /?-toluenesulfonic acid in acetic acid, laurinterol (31a) and isolaurinterol (33a) were converted to aplysin (27); debromolaurinterol (32a) was
transformed into debromoaplysin (26). Furthermore, lithium aluminum
hydride effected the change from laurinterol (31a) into debromolaurinterol
(32a), which in turn could be converted to laurinteryl acetate (31b) with
bromine in acetic acid.
The acid-catalyzed rearrangement of laurinterol derivatives was studied
in greater detail. Irie and co-workers (1969) noted that with /?-toluenesulfonic
acid in acetic anhydride rather than acetic acid debromolaurinteryl acetate
(32b) furnished not debromoaplysin (26), but compound 34, which, however,
could be further transformed to debromoaplysin (26) with /7-toluenesulfonic
acid in acetic acid.
In a follow-up study of the acid-catalyzed rearrangements of laurinterol
derivatives Suzuki et al. (1969) observed that laurinterol methyl ether (31c)
when treated with p-toluenesulfonic acid in acetic acid led only to recovery
of starting material. When the same compound (31c) was treated with 10%
sulfuric acid in acetic acid, two racemized cyclopentene derivatives, 35 and
36, resulted in a ratio of about 3.5:1. Corresponding cyclopentene derivatives
were obtained when debromolaurinterol methyl ether (32c) was treated
analogously. Under varied reaction conditions no compounds other than
35 and 36 were found, but prolonged reaction times favored the cyclopentene
derivative represented by structure 35.
AcO
^MeO
34
35
The stereochemical assignment of laurinterol as shown in 31 was determined by single-crystal X-ray diffraction of laurinteryl acetate, 31b (Cameron
et al, 1967). In their full paper the crystallographers (Cameron et al, 1969)
further state that the boat conformation is preferred for laurinteryl acetate.
The absolute configuration at the asterisked carbon in 31 has been related to
the corresponding carbon in camphor (37) in the following manner. Irie et al
(1967) converted laurene (29) into (+)-cuparene (38), which had been shown
by Enzell and Erdtman (1958) to have the same configuration at the starred
36
37
38
carbon as camphor (37), the absolute stereochemistry of which was proved
to be as depicted (Allen and Rogers, 1966). Cuparene (38) represents the
unrearranged farnesyl skeleton (structural type 25a) and has not been found
1. Isoprenoids
conversion of the three phenols to the corresponding aplysin derivatives. By
means of /?-toluenesulfonic acid in acetic acid, laurinterol (31a) and isolaurinterol (33a) were converted to aplysin (27); debromolaurinterol (32a) was
transformed into debromoaplysin (26). Furthermore, lithium aluminum
hydride effected the change from laurinterol (31a) into debromolaurinterol
(32a), which in turn could be converted to laurinteryl acetate (31b) with
bromine in acetic acid.
The acid-catalyzed rearrangement of laurinterol derivatives was studied
in greater detail. Irie and co-workers (1969) noted that with /?-toluenesulfonic
acid in acetic anhydride rather than acetic acid debromolaurinteryl acetate
(32b) furnished not debromoaplysin (26), but compound 34, which, however,
could be further transformed to debromoaplysin (26) with /7-toluenesulfonic
acid in acetic acid.
In a follow-up study of the acid-catalyzed rearrangements of laurinterol
derivatives Suzuki et al. (1969) observed that laurinterol methyl ether (31c)
when treated with p-toluenesulfonic acid in acetic acid led only to recovery
of starting material. When the same compound (31c) was treated with 10%
sulfuric acid in acetic acid, two racemized cyclopentene derivatives, 35 and
36, resulted in a ratio of about 3.5:1. Corresponding cyclopentene derivatives
were obtained when debromolaurinterol methyl ether (32c) was treated
analogously. Under varied reaction conditions no compounds other than
35 and 36 were found, but prolonged reaction times favored the cyclopentene
derivative represented by structure 35.
AcO
^MeO
34
35
The stereochemical assignment of laurinterol as shown in 31 was determined by single-crystal X-ray diffraction of laurinteryl acetate, 31b (Cameron
et al, 1967). In their full paper the crystallographers (Cameron et al, 1969)
further state that the boat conformation is preferred for laurinteryl acetate.
The absolute configuration at the asterisked carbon in 31 has been related to
the corresponding carbon in camphor (37) in the following manner. Irie et al
(1967) converted laurene (29) into (+)-cuparene (38), which had been shown
by Enzell and Erdtman (1958) to have the same configuration at the starred
36
37
38
carbon as camphor (37), the absolute stereochemistry of which was proved
to be as depicted (Allen and Rogers, 1966). Cuparene (38) represents the
unrearranged farnesyl skeleton (structural type 25a) and has not been found