Cirilo Pérez

New antimicrobial diterpenes from the sponge Spongia officinalis

Abstract The methanol extract of the sponge Spongia officinalis from Pt. Guimar, Tenerife (Canary Islands) contained new diterpenoids which inhibited the growth of microbes. The structures of the new diterpenes isolated were determined as; 11β-hydroxyspongi-12-en-16-one ( 2 ), 11β-acetoxyspongi-12-en-16-one ( 3 ), 7β,11β-dihydroxy8pongi-12-en-16-one ( 5 ), and 7β,11α-dihydroxy-spongi-12-en-16-one ( 6 ), by spectral and chemical degradation studies. The previously reported diterpenes isoagatholactone ( 1 ) and aplysillin ( 4 ) were also found in the extract.

Diterpenoids of mixed biogenesis in phaeophyta biogenetic-type interconversions☆

In the course of research into marine natural products, the diterpenoids taondiol 10 and atomaric acid 15, were isolated from the brown seaweed Taonia atomaria. The similarities of these structures plus the fact that both compounds come from the same alga suggest that there may be a biogenetic relationship between the two. This speculated relationship is adumbrated in Scheme 1, where the cyclic and acyclic diterpenoids of mixed biogenesis isolated from Phaeophyta are interrelated. In the present work, the competitive cyclisation of the proposed olefinic intermediate 4 to the naturally occurring compounds taondiol 10, isotandiol 11, epitaondiol 12 and stypodiol 13, is reported. The stereoselective transformation of atomaric acid 15 into the compound 4 is also reported, which transformation occurs by intramolecular carbocylisation of the olefinic aldehyde 7 followed by backbone rearrangement to the olefin 4. This result prompted the proposal that atomaric acid 15 may arise in nature by means of a like rearrangement but operating in a reverse direction.

Isocaespitol, a new halogenated sesquiterpene from Laurencia caespitosa

Abstract The halogenated sesquiterpene isocaespitol ( 1 ) has been isolated from the marine alga Laurencia caespitosa Lamx and its structure determined by X-ray crystallography.

Syntheses of marine molecules

The enantioselective total syntheses of (-)(E)ybisabolene-8,9-epoxide, (+) (2S,6R)-2-bromo-13-chamigrene, and (+)-chamigrene, important intermediates in the biosynthesis of natural sesquiterpenoids isolated from algae of the genus Laurencia, are described. The compounds are synthesized with regio nd stereocontrol by using simple forms of bridged intermediates. This represents a general strategy for the enantioselective construction of spirol5.5lundecane systems containing a chiral quaternary center. Our recent current progress towards the synthesis of the biologically active C25 tetronic acids isolated from sponges of the genus Ircinia is also described.

Total synthesis of 8-desoxy-isocaespitol, A new polyhalogenated sesquiterpene from Laurencia caespitosa☆

Abstract The structure of a new polyhalogenated bisabolene-type sesquiterpene, 2 , isolated from Laurencia caespitosa has been elucidated by chemical and spectral means and confirmed by a three-step synthesis starting from commercial farnesol.

New xenicane diterpenes from the brown algae of dictyotaceae

Two new xenicane diterpenes have been isolated from the brown algae of the Dictyotaceae family, and their structures and absolute configurations have been elucidated on the basis of their spectral and X-ray diffraction analyses

Total synthesis of obtusenol

Abstract The total synthesis of obtusenol ( 9 ), a dibrominated sesquiterpene isolated from the red alga Laupencia obtusa , has been achieved by a three-step synthesis starting from commercial farnesol.

Laurencia sesquiterpene biogenetic-type interconversions

Abstract Several aromatic sesquiterpenes from Laurencia algae were prepared from chamigrene skeleton precursors. Chemical evidence was adduced to support a biogenetic-type scheme for the synthesis of perforenol and perforene. By means of x ray analysis the structure and absolute configuration of one of the intermediates was established.

Three new triterpenes from the lichen Xanthoria resendei

Abstract The three new migrated hopene type triterpenes 12α-acetoxy-3β-hydroxyfern-9(11)-ene, 3β,12α-dihydroxyfern-9(11)-ene and 3,12-diketofern-9(11)-ene have been isolated from the ether extracts of the lichen Xanthoria resendei, together with peroxyergosterol and the anthraquinone pigments physcion, fallacinal and fallacinol.

A case of concomitant polymorphism and spontaneous resolution: the tetragonal phase of 5-hydroxymethyl-7,7,N-trimethyl-6-oxabicyclo[3.2.1]octane-1-carboxamide.

The title compound, C(12)H(21)NO(3), crystallizes in two polymorphic forms, viz. the tetragonal form described here and the monoclinic form described previously [Foces-Foces, López-Rodríguez, Pérez, Martín & Pérez-Hernández (2007). Cryst. Growth Des. 7, 905-911]. The differences in the conformations of the hydroxymethyl and methylaminocarbonyl substituents have important consequences in the hydrogen-bond interaction motifs and, therefore, in the packing arrangements. These forms are concomitant polymorphs with melting points differing by 3 K.