510
W. SANDERMANN
(CCCLXXVIII), etc. The well-known growth substance gibberellic acid
(CCCLXXXIII) is formed by splitting off of a methyl group and ring
contraction. The ring structure of atisine (CCCXCVI) can be thought
of as resulting from ring expansion in the phyllocladene skeleton. Simultaneous ring contraction and expansion leads to the delpheline skeleton
(CCCIC). Apart from the changes mentioned, others can, through dehydrogenation, lead to aromatic rings and to furans. The most important diterpene compounds known to date are shown in Table X.
E. TRITERPENES (I, 4, 5,
9-11)
The triterpenes, formed from six isopentane units, can be distinguished from each other on the basis of differences in their skeleton,
in the position of the ethylene linkages, or in the configuration of almost
20 substituent groups or subgroups (see Tables XI and XII). Squalene
(CDX) is entirely aliphatic, ambrein (CDXI) tricyclic, and the onocerin
group (CDXII) tetracyclic. A further large class of tetracyclic triterpenes has a skeleton similar to that of the steroids, and for this reason
they are referred to as steroid triterpenes. They can be subdivided into
the lanostane (CDI), euphol (CDU), and tirucallol (CDIII) groups.
The pentacyclic triterpenes include particularly the skeletons of ß-amyrin
(CDVI), α-amyrin (CDVII), lupeol (CDVIII), and friedelin (CDIX).
Recently representatives of the biogenetically interesting group of demethyl triterpenes (CDV) and a group with open ring A (CDIV) have
been found. The aromatic compound gossypol (DXV) should also be
included biogenetically among the triterpenes. For details of constitution, occurrence, and characteristics of the triterpenes, reference is made
to Tables XI, XII, and XVI.
W. SANDERMANN
(CCCLXXVIII), etc. The well-known growth substance gibberellic acid
(CCCLXXXIII) is formed by splitting off of a methyl group and ring
contraction. The ring structure of atisine (CCCXCVI) can be thought
of as resulting from ring expansion in the phyllocladene skeleton. Simultaneous ring contraction and expansion leads to the delpheline skeleton
(CCCIC). Apart from the changes mentioned, others can, through dehydrogenation, lead to aromatic rings and to furans. The most important diterpene compounds known to date are shown in Table X.
E. TRITERPENES (I, 4, 5,
9-11)
The triterpenes, formed from six isopentane units, can be distinguished from each other on the basis of differences in their skeleton,
in the position of the ethylene linkages, or in the configuration of almost
20 substituent groups or subgroups (see Tables XI and XII). Squalene
(CDX) is entirely aliphatic, ambrein (CDXI) tricyclic, and the onocerin
group (CDXII) tetracyclic. A further large class of tetracyclic triterpenes has a skeleton similar to that of the steroids, and for this reason
they are referred to as steroid triterpenes. They can be subdivided into
the lanostane (CDI), euphol (CDU), and tirucallol (CDIII) groups.
The pentacyclic triterpenes include particularly the skeletons of ß-amyrin
(CDVI), α-amyrin (CDVII), lupeol (CDVIII), and friedelin (CDIX).
Recently representatives of the biogenetically interesting group of demethyl triterpenes (CDV) and a group with open ring A (CDIV) have
been found. The aromatic compound gossypol (DXV) should also be
included biogenetically among the triterpenes. For details of constitution, occurrence, and characteristics of the triterpenes, reference is made
to Tables XI, XII, and XVI.