Spirocaracolitones, CD-Spiro Triterpenoids from Ruptiliocarpon caracolito

Abstract

Six CD-spiro-triterpenoids have been isolated and identified from the methylene chloride soluble extracts of the bark of Ruptiliocarpon caracolito. The structures of these compounds, named spirocaracolitones A−F, were determined by a combination of X-ray and high field NMR studies. The spirocaracolitones represent the first examples of a class of triterpenes which have a spiro system connecting rings C and D; they also carry an unusual 12-α-methyl group. It is postulated that these compounds are derived biogenetically from a friedelin derivative. Initial biological screening revealed up to 80% decreases in the rate of growth of the larvae of the European corn borer when these compounds were administered at the rate of 50 ppm in the diet.

Synthesis of spiro-cyclics via ring-closing metathesis

“…fluorene 7 and anthrone 8) as our substrates. 4 ] in THF at RT for 1 h (Scheme 1) to give the diallyl dione 9. Similarly, the preparation of the other diallyl derivative 10 was achieved by following the above general procedure, whereas compound 11 was prepared by using DBU as a base during the alkylation step.…”

“…Many natural products such as fredericamycin 1 1 (Figure 1), spirovetivanes, acroanes, chamigrenes, 2 angularly fused cyclopentanoids (e.g. crinipellin-A, laurenene) 3 and spirocaracolitone A 2 4 have shown to posses spiro-linkage as a structural element. 5 Among non-natural products [5.5.5.5]fenestrane 3, 6 spiranes, 7 and coronane 4 posses the spiro-linkage 8a,b as a crucial unit.…”

Spirocaracolitone Triterpenoids from the Bark of Ruptiliocarpon caracolito

“…In spirocaracolitones E and F, the C3-C4 bond in ring A had undergone oxidative cleavage to a dimethyl ester (Figure 3) The structures of spirocaracolitones A and E were confirmed by single-crystal X-ray diffraction. 2 The rings A and B methyl group pattern indicated that these compounds belong to the friedelin family of triterpenes. A possible biogenetic pathway for the genesis of the spiro system was proposed involving generation of a C-12 carbocation in the friedelin skeleton, migration of the C-13 methyl group, thereby generating a new cation at C-13, followed by migration of the C-8-C-14 bond.…”

“…A possible biogenetic pathway for the genesis of the spiro system was proposed involving generation of a C-12 carbocation in the friedelin skeleton, migration of the C-13 methyl group, thereby generating a new cation at C-13, followed by migration of the C-8-C-14 bond. 2 This sequence, shown in Scheme 1, accounts for the relative configuration of the ring junctions and methyl groups. Canophyllol, 4 a friedelin-type triterpene, 5 was also isolated from the same extracts.…”

“…Several years ago, we reported our initial phytochemical investigations of Ruptiliocarpon caracolito , a unique American species belonging to the family Lepidobotryaceae. , This species, which is endemic to the Osa peninsula of southwestern Costa Rica, belongs to one of only two genera of this family. The other is found in West Africa .…”