J.D. Martín

Non-terpenoid C-15 metabolites from the red seaweed Laurencia pinnatifida☆

Abstract The structures of absolute configurations of the halogenated vinyl acetylenes which are natural products from the red alga Laurencia pinnatifica (Gmal. Lamour) are described. The structure of trans - pinnatifidenyne 2 was determined by spectral, chemical and X-ray diffraction analyses. The structure of cis -pinnatifidenyne 1 is based on spectral comparison and chemical interconversion with the trans -isomer 2 . The structure of the acyclic trienyne 8 was secured as: (6 R ,7 R )-3- cis , 9- cis ,12- cis ,6-acetoxy,7-chloropentadeca-3,9,12-trien-1-yne by synthesis from cis -pinnatifidenyne 1 . The reactivity of these compounds to various conditions of catalytic hydrogenation has been examined in detail.

Terpenoids of the red alga laurencia pinnatifida

Abstract The structures of three brominated terpenoids which are natural products from the red alga Laurencia pinnatifida (Gmal. Lamour) are described. The structures of the sesquiterpenes 4 and 5 were determined by spectral comparison and chemical interconversion. The structure of the squalene-derived terpenoid 8 was secured by chemical transformation into thyrsiferol, a brominated triterpene previously isolated from the red alga Laurencia thyrsifera.

Marine natural products of the atlantic zone—V: The structure and chemistry of taondiol and related compounds

The structure of taondiol (1), a new aromatic terpenoid compound isolated from the marine alga Taonia atomaria (Dyctiotaceae) is elucidated and its biogenesis discussed. 1 1′-Desoxy-taondiol methyl ether (7) has been synthesized.

Biomimetic approach to the synthesis of rhodolaureol and rhodolauradiol

Abstract It is postulated that 9-hydroxy-β-iso-obtusene ( 4 ) is the biogenetic precursor of the tricyclic sesquiterpenoids rhodolauradiol ( 7 ) and rhodolaureol ( 9 ). The transformation 4 → 7 was carried out under non-enzymic conditions.

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.

Synthesis of cyclic ethers via 5-exo iodonium assisted epoxide ring expansion

The transannular cyclization of (Z,Z)-1-hydroxy-cyclonona-2,6-diene by iodonium assisted oxirane ring expansion was studied. The regioselectivity for the [4.3.1] vs [5.2.1] 10-oxabicyclo decane skeletons is high, and the iodine addition is also highly trans-selective. The results are rationalized in terms of a tricyclic oxonium ion intermediate.

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.

Carbon-13 NMR application to Laurencia polyhalogenated sesquiterpenes☆

By examining the chemical shifts of the carbons involved in vicinal trans-bromo-chloro systems, which are frequently isolated from Laurencia sesquiterpenes, it is possible to establish the position of the Br and Cl atoms beyond a doubt. This method was used in the structure determination of the new terpenoids, obtusane 3) and isofurocaespitane (17).

Tricyclic oxonium-directed addition: Regiochemistry and stereochemistry of the electrophilic additions to epoxy cycloalkenols.

The regio- and stereochemistry of electrophile-promoted transannular ring expansion of cyclo 1,5- and 1,6-epoxyalkenes and cyclo trans-1,5-bisepoxides were studied. The results are rationalized in terms of tricyclic oxonium intermediates showing the directing ability of oxygen substituents in the regio- and stereocontrol observed.

A new diterpene fromAplysia dactylomela

Abstract From the digestive gland of the sea hare Aplysia dactylomela a new trioxygenated diterpene possessing the dolabellane skeleton was isolated. The structure was solved by spectral properties and X-ray diffraction analysis.