A New Chamigrane from Laurencia glomerata

Abstract

From the red alga Laurencia glomerata four halogenated chamigranes have been isolated, one of which is new. The new metabolite, 4,10-dibromo-3-chloro-7,8-epoxy-9hydroxy-a-chamigrane [4] was identified by spectroscopic methods.Numerous chamigranes have been isolated from the red seaweed genus Laurencia which grows in many geographical areas (1-5). In a first examination of a South African species, L. glomerata Kiitz. (Rhodomelaceae), we have again encountered a group of chamigranes of which one is new.

Conformational Studies of Marine Polyhalogenated α‐Chamigrenes Using Temperature‐Dependent NMR Spectra. Cyclohexene‐ring flipping and rigid‐chair cyclohexane ring in the presence of equatorial halogen atoms at C(8) and C(9)

“…Thus, in the case of epoxide (+)-25, which is structurally related to (+)-7 and where, to maintain the Br-atom at C(2) in the equatorial position, Me-C(5) must be pushed away from H-C(8), the latter proton resonates at 6 4.78 (J = 13.1, 5.3), whereas in the case of the diastereoisomeric 26, where, for the same reasons, Me-C(5) must point toward H-C(8), the latter proton resonates at 6 4.88 (J = 12. 7, 5.6) [14]. Similar conclusions can be drawn for the epoxides of (-)-6: H-C (8) (5) pointing toward H-C (8)).…”

“…Our study allows to draw a number of other generalizations concerning the conformational behavior of a -chamigrenes: a ) the population ratio of conformers depends primarily on the spatial position (pseudoequatorial 0s. pseudoaxial) of the substituents at the two available positions of ring A (C(2) and C (3) where, for the same reasons, Me-C(5) must point toward H-C (8), the latter proton resonates at 6 4.88 (J = 12.7, 5.6) [14]. Similar conclusions can be drawn for the epoxides of (-)-6: H-C(8) resonates at 6 4.77 (J = 12, 5) for the natural epoxide with cis-related Br-atom and epoxide group (Me-C(5) pointing away from H-C (8)) [15a] or at 6 4.88 (J = 11, 7) for the semisynthetic [lsa] or natural [15b] diastereoisomer with trans-related Br-atom and epoxide group (Me-C(5) pointing toward H-C (8)).…”

“…That work included rogiolol acetate ((+)-l), rogiolol ((-)-2), obtusol ((+)-3), and obtusol acetate ((-)-4) [ 11. The energy barrier to these motions was attributed to mainly repulsive interactions between H,-C (14) and the axial H-atoms at C (8) and C(10). We observed also that the conformer involving steric compression between Br-C(2) and H,-C(7) was thermodynamically so much disfavored to escape direct detection by NMR.…”

Molecular networking prospection and characterization of terpenoids and C15-acetogenins in Brazilian seaweed extracts

“…Loss of H 2 O [C 15 H 21 Br 2 ClO 2 À H 2 O + H] + (calcd m/z 428.9654). These data were also indicative of a chamigrane-type sesquiterpene, and this compound was suggested to be pacifenol (27), since MS data and RT were in agreement with those from pacifenol isolated from LC1 (L. catarinensis from Xavier Island). This metabolite was reported for some Laurencia species, such as L. liformis, 38 L. majuscula 39 and L. pacica.…”

Progress in the Chemistry of Organic Natural Products 102

“…These, by inhibiting transport proteins like P-gp that are overexpressed in lactating mammary tissues [88,89] could interfere with the transfer of diterpenoids from plasma to milk, potentially exacerbating the toxicity of spurges (see Sect. Also the larvae of some moths can feed with impunity on Euphorbia species, accumulating toxic phorboids in their body and carrying them into adult life as a protection against predators [90]. Also the larvae of some moths can feed with impunity on Euphorbia species, accumulating toxic phorboids in their body and carrying them into adult life as a protection against predators [90].…”