A New-Skeleton Diterpenoid, New Prenylbisabolanes, and Their Putative Biogenetic Precursor, from the Red SeaweedLaurencia microcladia from Il Rogiolo: Assigning the Absolute Configuration when Two Chiral Halves are Connected By Single Bonds

Abstract

We report here a new-skeleton tricyclic diterpenoid, neorogioldiol (8), along with new prenylbisabolanes, rogioldiol D (6) and O 11 , 15-cyclo-14-bromo-14,15-dihydrorogiol-3,11-diol (5), and their putative biogenetic precursor, (À)-geranyllinalool (7), isolated from the red seaweed Laurencia microcladia, which has colonized a small tract of the Tuscany coast called Il Rogiolo. In a case study of the assignment of the absolute configuration for molecules composed of chiral halves that are connected by single bonds, the absolute configuration of neorogioldiol (8) was based on a) the assumption of the identity of the cyclohexane moiety with co-occurring (2S,3R,6S)-rogiolal (4) and b) NMR-derived relative configurations for the bicyclic moiety, and c) the combination of these two pieces of information by molecular-mechanics-aided conformational analysis, in agreement with NOE data.

ent-Labdane diterpenes from the aquatic plant Potamogeton pectinatus

“…They consisted of a lignan, pinoresinol (8) (Agrawal and Thakur, 1985), a linear diterpene, (3S)-geranyllinalool (9) (Guella and Pietra, 2000) and d-tocopherol (10) (Matsuo and Urano, 1976;Vieira et al, 1983).…”

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

“…45 Furthermore, L. microcladia from some Greek islands showed different chemical proles according to the collection sites. [46][47][48][49] No compound could be identied in the extracts of Dictyopteris spp., Laurencia dendroidea and L. intricata.…”

Progress in the Chemistry of Organic Natural Products 102

“…In 2003, the same group published the structures of prevezols C (618), D (619), and E (620), obtained from another population of L. obtusa collected again from Preveza, while prevezol B (617) was re-isolated and its structure revised [528]. L. microcladia collected from Il Rogiolo, Italy, yielded neorogioldiol (621) [532], whereas its epimer at C-11, neorogioldiol B (622), was isolated from L. obtusa collected from Preveza [528]. Comparison of the spectroscopic data of the natural products 617 and 618 with those of the products obtained through total syntheses of the proposed structures for prevezols B [529] and C [530], respectively, exhibited slight discrepancies, albeit without suggesting alternative structures for the natural products.…”

“…In addition to the diterpenes belonging to the classes discussed above, there are 22 more diterpenes (637), isolated from L. microcladia from Il Rogiolo [532], feature a prenylated bisabolane skeleton. The latter compound exhibits an etherification between carbons C-11 and C-15, while both 636 and 637 display a cis-1,2-bromohydrin moiety in their structures.…”