The vibrational spectra of cis,cis-,trans,trans- and cis,trans-1,4-dichloro-1,3-butadiene

The i.r. spectra of cis,cis,trans,_trans and cis,trans-1,4-dichloro-1,3-butadiene were recorded in cyclohexane solution in the region 600-40 cm⁻¹. Raman spectra, including polarization measurements of the neat liquids were obtained. Some previously unobserved fundamentals, particularly in the low frequency region, were assigned, and a few revisions in the earlier interpretations were made.Force fields containing 21 parameters for the cis,cis and the trans,trans compounds were constructed by transferring force constants from cis- and trans-1-chloro-1,3-butadiene. By mixing the force constants from these monochlorobutadienes a 29 parameter force field was derived for the cis,trans compound. The calculated r.m.s. amplitudes of vibration and perpendicular amplitude correction coefficients are presented.     

Total synthesis of five proline-enriched cyclic heptapeptides from the marine sponge Stylissa carteri

The total synthesis of five naturally occurring cyclic proline-enriched heptapeptides from the marine sponge Stylissa carteri was reported. The five cyclic heptapeptides were synthesized by applying a two-step solid-phase/solution synthesis strategy. The linear heptapeptides were assembled by standard Fmoc chemistry on 2-chlorotrityl chloride resin, cleaved off-resin with acetic acid/trifluoroethanol/dichloromethane to keep side-chain protecting groups intact, and subsequently cyclization was achieved by a solution method. The final products were purified by a preparative RP-HPLC system, and their structures were characterized by HR-QTOF-MS NMR. The spectral data of synthetic peptides were found to be identical to that reported for the natural products.     

Halioxepine, a new meroditerpene from an Indonesian sponge Haliclona sp

Chemical investigations on a sponge Haliclona sp. found a meroditerpene 1 having a new carbon skeleton. By analyzing spectroscopic data, the structure was elucidated to comprise a substituted hydroquinone, a tetrahydrooxepine, and a cyclohexene, and these components were united with C1 and C2 units. Compound 1 showed moderate cytotoxicity against NBT-T2 cells with IC50 4.8 μg/ml and also antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) with IC50 3.2 μg/ml.     

Synthetic studies toward bioactive cyclic peroxides from the marine sponge Plakortis angulospiculatus

[reaction: see text] The total synthesis of two stereoisomers of a bioactive cyclic peroxide isolated from the marine sponge Plakortis angulospiculatus has been achieved in 18 steps with an overall yield of 2.8%. Diels-Alder addition of singlet oxygen to an acyclic triene carboxylic acid precursor was used to construct the 3,6-dihydro-1,2-dioxin ring. By comparing spectral data of the synthesized compounds and the natural material, we tentatively assign the absolute stereochemistry for the natural product as 3S,6R,8S,10R.     

Honulactones: new bishomoscalarane sesterterpenes from the Indonesian sponge Strepsichordaia aliena

From the dichloromethane/2-propanol (1:1) extract of the Indonesian marine sponge Strepsichordaia aliena, twelve new 20, 24-bishomoscalarane sesterterpenes, honulactones A-L (1-12) were isolated. Molecular structures were secured by spectroscopic methods, accurate mass measurements, and X-ray analysis. Honulactones A (1), B (2), C (3), and D (4) exhibit cytotoxycity against P-388, A-549, HT-29, and MEL-28 (IC(50) 1 microg/mL).     

Scytalidamides A and B, new cytotoxic cyclic heptapeptides from a marine fungus of the genus Scytalidium

Two new cyclic heptapeptides have been isolated from the culture broth of a marine fungus, Scytalidium sp., collected from the Bahamas. The planar structures of scytalidamides A (1) and B (2) were assigned on the basis of 1D and 2D NMR spectroscopic techniques, while the absolute configuration of the amino acid residues in both molecules was determined by application of the advanced Marfey's method. The absolute stereochemistry of the uncommon 3-methylproline moiety in scytalidamide B (2) was confirmed by isolation and CD measurements, as well as application of the advanced Marfey's method. Scytalidamides A (1) and B (2) showed moderate in vitro cytotoxicity toward HCT-116 human colon adenocarcinoma with IC(50) values of 2.7 and 11.0 microM, respectively.     

Diacarperoxide S, new norterpene cyclic peroxide from the sponge Diacarnus megaspinorhabdosa

Re-investigation of the methanolic extract of the sponge Diacarnus megaspinorhabdosa afforded one new norsesterpene cyclic peroxide diacarperoxide S (2), in addition to two known compounds sigmosceptrellin B (1) and nebularine (3). The structures of the isolated compounds were established on the basis of one and two dimensional NMR spectroscopic studies (1H, 13C, DEPT, COSY, HMQC, HMBC, and ROESY) as well as on mass spectral analysis. The isolated compounds were evaluated for their cytotoxic as well as antimicrobial activities.     

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.     

Laureepoxide,new bromo ether from the marine red alga Laurencianipponica Yamada

An interesting bromine containing compound, laureepoxide ($\text{1}$), has been isolated from $\text{L}$. $\text{nipponica}$ Yamada (Rhodomelaceae, Rhodophyta) and its structure has been determined by the chemical degradations and spectral properties.     

Metal-organic frameworks from copper dimers with cis- and trans-1,4-cyclohexanedicarboxylate and cis,cis-1,3,5-cyclohexanetricarboxylate

Single crystals of three coordination networks containing the Cu(2)(COO)(4) core bridged by cyclohexane have been hydrothermally prepared by the reaction of 1,4-cyclohexanedicarboxylic (1,4-H(2)chdc) or 1,3,5-cyclohexanetricarboxylic (1,3,5-H(3)chtc) acid and Cu(NO(3))(2) x 6H(2)O. We report their characterizations by single-crystal X-ray structure determinations, IR spectroscopy, thermal analyses, and their magnetic properties. [Cu(2)(trans-1,4-chdc)(2)] (1) consists of 4 x 4 grids with the dimeric nodes connected by the trans-1,4-chdc, and these grids are then connected to each other by Cu-O bonds, resulting in a porous network (void volume of 130 Angstrom(3) per cell or 25%) with no solvent in its cavities. [Cu(2)(cis-1,4-chdc)(2)(H(2)O)(2)] (2) consists of two-legged ladders where the dimer nodes are bridged by pairs of cis-1,4-chdc and the water molecules cap the ends of the Cu dimers. [Cu(2)(1,3,5-Hchtc)(2)] (3) displays 4 x 4 grids, but each dimeric node is connected to its neighbors within the same grid by Cu-O bonds to form a layered network which further makes hydrogen-bond interactions with its neighbors. 2 and 3 have compact structures without any space for solvents. IR and DT-TGA confirm the absence of water in the empty channels of 1, while IR shows the presence of both protonated and deprotonated carboxyl groups for 3. The magnetic properties of all three compounds are dominated by the strong Cu-Cu antiferromagnetic interaction resulting in singlet-triplet gaps of 450-500 K.     

Laurenidificin, a new brominated C15-acetogenin from the marine red alga Laurencia nidifica

<正>A new brominated C_(15)-acetogenin,namely,laurenidificin,was isolated from the marine red alga Laurencia nidifica.Its structure was determined on the basis of spectroscopic methods.     

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.     

Two new brominated C15-acetogenins from the red alga Laurencia japonensis

Abstract

We report on the chemical characteristics of the red alga Laurencia japonensis, collected off the coast of Yoshio, Katsuura, Boso Peninsula, Japan. We isolated two new brominated C₁₅-acetogenins in this species, which we name katsuurenyne A (1) and katsuurenyne B (2), along with two already known halogenated terpenes [2,10-dibromo-3-chloro-α-chamigrene (7) and aplysiadiol (8)]. We extensively analysed spectral data (from IR, ESI-MS, 1D-NMR and 2D-NMR) to confirm the structure of these compounds.