Defense Allomones of the Nudibranch Phyllidia varicosa Lamarck 1801

Abstract

The defensive secretion of the nudibranch Phyllidia varicosa consists of two isocyanosesquiterpenes: the previously described 9‐isocyanopupukeanane (1), and its 2‐isomer (4), for which we report the structure and properties. The mixture originates with a sponge, Hymeniacidon sp., where it is produced in varying proportions. CD. measurements and X‐ray diffraction data establish the absolute configuration of the two metabolites.

Chloropupukeanolides C–E: Cytotoxic Pupukeanane Chlorides with a Spiroketal Skeleton from Pestalotiopsis fici

“…; [27,28] the C9 epimer of 9-isocyanopupukeanane from the nudibranch P. bourguini; [29] 2-thiocyanatopupukeanane from a Palauan sponge of Axinyssa aplysinoides; [30] 9-isothiocyanatopupukeanane from the sponge Axinyssa sp. [31] Some neopupukeananes have also been isolated from marine sponges, such as 2-and 4-thiocyanatoneopupukeanane [30,32] and 9-isocyanoneopupukeanane. [33] Prior to the discovery of chloropupukeananin (1), [15] chloropupukeanolides A (5) and B (6), [19] and chloropupukeanone A (7), [19] the only example with a tricyclo-[4.3.1.0 3,7 ]-decane carbon skeleton from terrestrial sources was nemorosonol, a polyisoprenylated pupukeanane from the fruits of the South-American plant Clusia nemorosa and the leaves of the Vietnamese plant Garcinia bracteata (both of the Clusiaceae family).…”

“…[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] Examples include: 2-and 9-isocyanopupukeanane, the marine invertebrate allomones isolated from the nudibranch Phyllidia varicosa and its prey, a sponge Hymeniacidon sp. ; [27,28] the C9 epimer of 9-isocyanopupukeanane from the nudibranch P. bourguini; [29] 2-thiocyanatopupukeanane from a Palauan sponge of Axinyssa aplysinoides; [30] 9-isothiocyanatopupukeanane from the sponge Axinyssa sp. [31] Some neopupukeananes have also been isolated from marine sponges, such as 2-and 4-thiocyanatoneopupukeanane [30,32] and 9-isocyanoneopupukeanane.…”

Marine isocyano compounds

“…Biogenetically, the various skeletal types, including the complex tricyclic pupukeananes (eg., 76), may be derived from cationic or cationic-equivalent intermediates of terpene origin. Recent isolation of five previously known isonitriles, 53,76,77,85,88, coupled with the isomeric amorphene, 36, and aUopupukeanane, 79, by Fusetani et aL [43] is consistent with the biogenetic relationship of the pupukeananes with the amorphane type skeletons [54].…”

“…Single crystal X-ray diffraction analysis of 78 confirmed its structure as a regioisomer of 76. Transformation of isonitrile 76, but not the hindered 78, to the corresponding 9-ketone permitted assignment of the absolute configuration of both compounds [53]. Both isocyano-pupukeananes 76 and 78 were the first marine isonitriles to be synthesized (cf.…”

“…Following field and laboratory observations by Johannes [70], Burreson linked the dietary source of P. varicosa to a sponge (15,53) later identified as Ciocalypta sp. In view of the small size and scarcity of the nudibranch, this crucial observation eventually resulted in isolation and GC comparison of the constituents derived from Ciocalypta and P. varicosa.…”