Progress in the Chemistry of Cytochalasans
53
IFB-E019. Following this, ten chaetoglobosins (310–319) belonging to this same
group have been reported, with all of these isolated from the fungus Chaetomium
globosum. Moreover, chaetomadrasin B (319) [129] from Chaetomium madrasense
375 represents the first example of a chaetoglobosin characterized by possessing
both a hydroxy and a carbonyl group on the indole moiety.
• [5.6.7.5]- and [5.6.12]-Chaetoglobosins
Armochaeglobines A (320) and B (321) [147], two chaetoglobosins with unprecedented carbon skeletons, were also obtained from the fungus Chaetomium globosum
TW1-1, of which armochaeglobine A (320) features a unique tetracyclic 5/6/7/5
fused ring system and armochaeglobine B (321) possesses a rare 12-membered
carbon scaffold. Both compounds represent the first examples of chaetoglobosins
with an even-numbered (10- and 12-) carbocyclic ring C, differing from those of
other cytochalasans by having a 9-, 11-, 13-, or 15-membered carbocyclic ring C.
In particular, armochaeglobine A (321) possesses an unusual peroxide functionality in ring B. Their biosynthesis pathways were proposed starting from chaetoglobosin A (210), which undergoes oxidation, Michael addition, electrophilic addition,
decarboxylation and peroxidation, and aldol condensation reactions.
[5.6.11]-Chaetoglobosins
Both [5.6.11]-cytochalasins and [5.6.11]-pyrichalasins are the main types in their
respective groups; however, [5.6.11]-chaetoglobosins (Table 12 and Fig. 12) represent a minor variant among the chaetoglobosin analogs. Four chaetoglobosins have
been found to possess the [5.6.11] ring system, namely, cytochalasin G (322) [149]
and cytochalasins X–Z (323–325) [150]. Cytochalasin G (322) [149] was the first
[5.6.11]-chaetoglobosin to be isolated and was obtained by Cameron and coworkers
from a Nigrosabulum sp. in 1974. Almost 30 years later, in 2002, Munro and
coworkers re-isolated this compound from Pseudeurotium zonatum, along with three
new [5.6.11]-chaetoglobosins named cytochalasins X–Z (323–325) [150]. Nearly
20 years since then have passed, and still today, these four compounds remain the
only naturally occurring chaetoglobosins containing an 11-membered macrocycle.
2.3.2 seco-Chaetoglobosins
The first seco-chaetoglobosins, armochaetoglobins A–E (326–330) [124], were
reported by Zhang and coworkers in 2015 from the fungus Chaetomium globosum
TW1-1. From this same fungus, a series of pyrrole-chaetoglobosins was also isolated,
as mentioned previously. Interestingly, armochaetoglobin A (326), as an unprecedented 19,20-seco-chaetoglobosin, also contains a pyrrole ring. All these compounds
possibly are derived from normal chaetoglobosins or pyrrole-chaetoglobosins by the
53
IFB-E019. Following this, ten chaetoglobosins (310–319) belonging to this same
group have been reported, with all of these isolated from the fungus Chaetomium
globosum. Moreover, chaetomadrasin B (319) [129] from Chaetomium madrasense
375 represents the first example of a chaetoglobosin characterized by possessing
both a hydroxy and a carbonyl group on the indole moiety.
• [5.6.7.5]- and [5.6.12]-Chaetoglobosins
Armochaeglobines A (320) and B (321) [147], two chaetoglobosins with unprecedented carbon skeletons, were also obtained from the fungus Chaetomium globosum
TW1-1, of which armochaeglobine A (320) features a unique tetracyclic 5/6/7/5
fused ring system and armochaeglobine B (321) possesses a rare 12-membered
carbon scaffold. Both compounds represent the first examples of chaetoglobosins
with an even-numbered (10- and 12-) carbocyclic ring C, differing from those of
other cytochalasans by having a 9-, 11-, 13-, or 15-membered carbocyclic ring C.
In particular, armochaeglobine A (321) possesses an unusual peroxide functionality in ring B. Their biosynthesis pathways were proposed starting from chaetoglobosin A (210), which undergoes oxidation, Michael addition, electrophilic addition,
decarboxylation and peroxidation, and aldol condensation reactions.
[5.6.11]-Chaetoglobosins
Both [5.6.11]-cytochalasins and [5.6.11]-pyrichalasins are the main types in their
respective groups; however, [5.6.11]-chaetoglobosins (Table 12 and Fig. 12) represent a minor variant among the chaetoglobosin analogs. Four chaetoglobosins have
been found to possess the [5.6.11] ring system, namely, cytochalasin G (322) [149]
and cytochalasins X–Z (323–325) [150]. Cytochalasin G (322) [149] was the first
[5.6.11]-chaetoglobosin to be isolated and was obtained by Cameron and coworkers
from a Nigrosabulum sp. in 1974. Almost 30 years later, in 2002, Munro and
coworkers re-isolated this compound from Pseudeurotium zonatum, along with three
new [5.6.11]-chaetoglobosins named cytochalasins X–Z (323–325) [150]. Nearly
20 years since then have passed, and still today, these four compounds remain the
only naturally occurring chaetoglobosins containing an 11-membered macrocycle.
2.3.2 seco-Chaetoglobosins
The first seco-chaetoglobosins, armochaetoglobins A–E (326–330) [124], were
reported by Zhang and coworkers in 2015 from the fungus Chaetomium globosum
TW1-1. From this same fungus, a series of pyrrole-chaetoglobosins was also isolated,
as mentioned previously. Interestingly, armochaetoglobin A (326), as an unprecedented 19,20-seco-chaetoglobosin, also contains a pyrrole ring. All these compounds
possibly are derived from normal chaetoglobosins or pyrrole-chaetoglobosins by the