Laurallene,new bromoallene from the marine red alga Laurencia nipponica Yamada

Laurallene ($\text{1}$), a new brominated cyclic ether having a terminal allene moiety, has been isolated as a main constituent from the marine red alga $\text{Laurencia nipponica}$ Yamada (Rhodomelaceae, Rhodophyta) and its structure was determined by its physical and chemical properties.     

Okamurallene,a novel halogenated C15 metabolite from the red alga laurencia okamuhai yamada

Okamurallene ($\text{1}$), a novel nonterpenoid C₁₅ bromoallene containing cyclopropane ring, has been isolated from the red alga Laurencia okamurai Yamada and its structure was determined by the spectral evidence.     

Two new C15 acetylenes from the marine red alga laurencia obtuse

Two new brominated C₁₅,-nonterpenoids which are unusual oxolane derivatives possessing a propargylic bromide side chain have been isolated from the red alga $\text{L. obtuse}$ and their structures were determined as 6 and 7. The ¹HNMR spectra of these new compounds are presented and assignments made.     

A new labile bromoterpenoid from the red alga laurencia majuscula: Dehydrochloroprepacifenol

A new labile brominated chamigrene, dehydrochloroprepacifenol, was isolated from the red alga Laurencia majucula. The structure of this compound was determined by its spectral properties and low-temperature X-ray diffraction analysis.     

Structures and absolute stereochemistry of nipponallene and neonipponallene, new brominated allenes from the red alga Laurencia nipponica

Two new natural brominated allenes named as nipponallene 1 and neonipponallene 2 were isolated from the red alga Laurencia nipponica, collected near the Russian shore of the Sea of Japan (Troitsa Bay). The structures and absolute stereochemistry of 1 and 2 were elucidated using NMR spectroscopy, chemical transformations, modified Mosher’s method and on the basis of biogenetic understanding.     

(10R̃, 11R̃)-(+)-squalene-10, 11-epoxide: Isolation from Laurencia okamurai and the asymmetric synthesis

From a red alga $\text{Laurencia okamurai}$ (10$\text{R}\text{?}$, 11$\text{R}\text{?}$)-(+)-squalene-10, 11-epoxide $\text{1}\text{?}$ was isolated and its asymmetric synthesis has been achieved starting from $\text{trans, trans}$-farnesol.     

Palisadins A,B and related monocyclofarnesol-derived sesquiterpenoids from the red marine alga Laurencia cf. palisada

Five new monocyclofarnesol-derived sesquiterpenoids, along with the previously reported lactone aplysistatin, have been isolated from the tropical red alga $\text{Laurencia}$ cf. $\text{palisada}$. The structures of these new compounds were defined by spectral and chemical analyses, including their partial interconversion with aplysistatin.     

Teurilene and thyrsiferyl 23-acetate, meso and remarkably cytotoxic compounds from the marine red alga laurencia obtusa (hudson) lamouroux

Two new cyclic ethers consisting of squalene carbon skeleton have been isolated from the red alga L. obtusa. The absolute stereostructure of teurilene ($\text{1}$) was elucidated by x-ray crystallographic method, and the structure of thyrsiferyl 23-acetate ($\text{2}$) was established from the spectral and chemical evidence.     

Isolation and structures of trans-laurencenyne,a possible precursor of the C15 halogenated cyclic ethers,and trans-neolaurencenyne from laurencia okamurai

Isolation and structural elucidation of two new acetylenic polyenes, $\text{trans}$-laurencenyne $\text{1}$ and $\text{trans}$-neolaurencenyne $\text{2}$ from the marine red alga $\text{Laurencia okamurai}$ were carried out, the former compound $\text{1}$ very recently being proposed to be a biosynthetic precursor of the C₁₅ halogenated cyclic ethers, $\text{7}$ and $\text{8}$.     

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 $\text{3}$) and isofurocaespitane ($\text{17}$).     

Aldingenin A, new brominated sesquiterpene from red algae Laurencia aldingensis

A new brominated bisabolene derivative, aldingenin A, was isolated from red alga Laurencia aldingensis Saito et Womersley (Ceramiales, Rodophyta). Its structure was determined by analysis of spectroscopic data (¹H and ¹³C NMR, IR, MS), including bidimensional NMR (¹H-¹H COSY, HMQC, HMBC and NOESY) and biogenetic considerations.     

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

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

Two new brominated diterpenes from Laurencia decumbens

Two new brominated diterpenes,namely,laurendecumtriol and 11-deacetylpinnaterpene C,were isolated and identified from the marine red alga Laurencia decumbens.Their structures were established on the basis of various NMR spectroscopic techniques and HR-ESI-MS analyses.     

The isolation of new norcycloartene triterpenoids from the tropical marine alga Tydemaniaexpeditionitis (chlorophyta)

Three new Δ³-norcycloartene triterpenoids, with differing side chain functionalities, have been isolated from the tropical green alga $\text{Tydemania}$$\text{expeditionitis}$ collected in Guam. The structures of these new compounds were secured by x-ray crystallography and by chemical interconversion.     

The structure of spirolaurenone,a halogenated sesquiterpenoid from the red alga laurencia glandulifera kützing

The structure of spirolaurenone (1), a halogenated metabolite isolated from the red alga Laurencia glandulifera Kützing, was determined on the basis of the chemical and spectroscopic evidence. The absolute configuration of spirolaurenone (1) was established as shown in formula 1 by the chemical correlation with glanduliferol (18), a halo-chamigrene derivative isolated from the same alga.     

Hybridalactone,An unusual fatty acid metabolite from the red alga Laurencia hybrida (Rhodophyta,Rhodomelaceae)

The structure of hybridalactone (10) an unusual C₂₀ fatty acid-derived metabolite from the red alga Laurencia hybrida has been assigned on the basis of spectroscopic data and results of chemical degradation experiments.     

Laurencenyne,a plausible precursor of various nonterpenoid C15-compounds,and neolaurencenyne from the red alga laurencia okamurai

Structural elucidation of two new acetylenic polyenes, laurencenyne $\text{5}$ and neolaurencenyne $\text{6}$ isolated from $\text{Laurencia okamurai}$, together with their syntheses, was achieved, suggesting that laurencenyne $\text{5}$ was a possible precursor of various nonterpenoid C₁₅-compounds in the marine red algae of the genus $\text{Laurencia}$.     

Terpenes and Polybromoindoles from the Marine Red Alga Laurencia decumbens (Rhodomelaceae)

Two new brominated diterpenes, namely, laurendecumtriol ( 1 ) and 11‐O‐deacetylpinnaterpene C ( 2 ), one new polybromoindole, 2,3,4,6‐tetrabromo‐1‐methyl‐1H‐indole ( 7 ), and six known natural products were isolated and identified from the marine red alga Laurencia decumbens. Their structures were elucidated on the basis of detailed spectroscopic and mass‐spectrometric analysis as well as by comparison with literature data. Based on 2D‐NMR experiments, the previously reported NMR data for pinnaterpene C ( 3 ) were reassigned.     

Saiyacenols A and B: the key to solve the controversy about the configuration of aplysiols

Two new cytotoxic oxasqualenoids, saiyacenols A and B, were isolated from the red alga Laurencia viridis and their structures elucidated by spectroscopic methods and chemical correlation with the well-known compound dehydrothyrsiferol. The new compounds share an important part of their structure with thyrsiferol and aplysiols B and C. Isolation of the saiyacenols concludes the controversy about the configuration of aplysiols, correcting the structure of aplysiol B. Our results illustrate the current limitations of NMR J-based methods when approaching quaternary carbons and demand a reappraisal of rational biogenetic proposals in structural elucidation.     

Total synthesis of obtusenol

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