A secoisolariciresinol branched fatty diester from Salvia plebeia seed

The structure of a second new lignan diester from Salvia plebeia seed has been determined. Hydrolysis of this diester yields two compounds, 12-methyltetradecanoic acid and secoisolariciresinol.     

Novel pyrrolizidine alkaloid from Crotalaria nana

Crotananine, isolated from the seeds of Crotalaria nana has been shown by spectroscopy and chemical evidence to be the macrocyclic diester of retronecine and a new C₉ necic acid, crotananic acid.     

Optical purity of (3S,3'S)-astaxanthin from Haematococcus pluvialis

Haematococcus pluvialis cultivated in a N-deficient medium produced astaxanthin (1 % of total carotenoids), the monoester (76 %) and diester (7 %) of astaxanthin, β,β-carotene (1 %), an adonirubin ester (3 %), (3R,3′R,6′R)-lutein (7 %), violaxanthin (2 %) and neoxanthin (1 %). The CD values of the mono- and diesters of astaxanthin, the HPLC properties of astaxanthin monoester further esterified with (?)-camphanic acid and the optical purity of astaxanthin [determined by HPLC analysis of the diester of(?)-camphanic acid] produced by saponification of the natural mono- and diesters of astaxanthin in the absence of oxygen showed that this green alga synthesizes pure (3S,3′S)-astaxanthin esters.     

Synthesis of mixed diesters of ethanediol with N-acyl amino acids and fatty acids

Chemical synthesis of mixed diesters of ethanediol with N-acyl amino acids and fatty acids is described. The synthesis is performed in three steps: (1) preparation of N-acyl amino acids using fatty acid ester of N-hydroxyphthalimide as an acylating agent; (2) partial esterification of ethanediol with N-acyl amino acid, in tetrahydrofuran in presence of thionyl chloride; (3) further esterification of the monoester of ethanediol with a fatty acid, to a mixed diester, in presence of the same reagent.     

Oestrogen and essential fatty acid supplementation corrects bone loss due to ovariectomy in the female Sprague Dawley rat

Essential fatty acid deficient animals develop osteoporosis. Eicosapentaenoic acid and gamma-linoleic acid have been reported to have positive effects on bone metabolism in both the growing male rat and the ovariectomized (OVX) female rat. These effects have been further investigated using a novel gamma-linolenic/eicosapentaenoic acid diester together with an oestrogen implant in the ovariectomized, female Sprague Dawley rat. Rats were sham-operated or ovariectomized at age 11 weeks. Two groups of OVX rats received an oestrogen implant at ovariectomy. Animals received fatty acids, linoleic acid (control) or a diester with gamma-linolenic acid and eicosapentaenoic acid as part of a semi-synthetic diet. Bone calcium content and excretion of deoxypyridinolines as marker of bone degradation were measured at 14 weeks. Oestrogen, as well as diester alone, increased calcium/femur to sham levels. Oestrogen plus diester potentiated the effect of oestrogen on bone calcium (P < 0.05 vs OVX). At the same time, oestrogen alone and the combination of oestrogen plus diester significantly reduced (P < 0.05 vs OVX) urinary deoxypyridinoline and hydroxyproline excretion. Again, the diester potentiated the effect of oestrogen. The effects of the diester alone, together with the potentiated effects of oestrogen by the essential fatty acids on osteoporosis, are novel findings.     

13C NMR spectroscopy of Pyrrolizidine alkaloids

The ¹³C NMR spectra of nine pyrrolizidine alkaloids of the macrocyclic diester type, seven of the corresponding N-oxides and of the parent base retronecine have been recorded and the signals assigned. The 13C NMR signals were found to be sensitive to structural variation in both the diester moiety and the heterocyclic ring system, providing useful information for structural elucidation, particularly when the ¹H NMR spectra may be difficult to interpret.     

Long chain esters of Virola species

The esters of n-fatty acids and ω-hydroxy n-fatty acids of β-sitosterol, D-glucose and ferulic acid (trans and cis) as well as β-sitosterol, fatty acids and β-sitosteryl-β-D-glucoside were isolated from three Virola species and identified by optical data and chemical reactions. A novel series of acidic esters derived from C₂₂C₂₉ ω-hydroxy fatty acids and cis- and trans-ferulic acid is reported for the first time. These compounds also occurred as the corresponding diester 1-monoglycerides whereas the ω-hydroxy acids themselves were also present as the corresponding glucosyl esters.     

Accumulation and enzymatic synthesis of 2-O-acetyl-3-O-(p-coumaroyl)-meso-tartaric acid in spinach cotyledons

2-O-Acetyl-3-O-[(E)-p-coumaroyl]-meso-tartaric acid was isolated from cotyledons of Spinacia oleracea and its structure elucidated and characterized with the aid of TLC, HPLC, FAB MS and ¹H NMR. Accumulation and enzymatic synthesis of the diester are described, proceeding first via 1-O-(p-coumaroyl)-β-glucose in the formation of p-coumaroyltartaric acid and second via acetyl-CoA in the formation of 2-O-acetyl-3-O-[(E)-p-coumaroyl]-meso-tartaric acid. Some properties of the CoA-thioester-dependent acyltransferase activity were studied.     

Free and esterified carotenoids in green and red fruits of Capsicum annuum

Fully green and mature red fruits of the Yolo Wonder A variety of Capsicum annuum were analysed for their carotenoid content. The disappearance of chlorophyll was followed by an increased synthesis of carotenoids. Lutein was not detected in the red fruit in which capsanthin was the main carotenoid. It appeared as diester, monoester and free forms, while capsorubin occured as a diester only. Cryptocapsin was not esterified.     

Iridoid and phenylethanoid glycosides in the New Zealand sun hebes (Veronica; Plantaginaceae)

The sun hebes are a small clade of New Zealand Veronica formerly classified as Heliohebe. The water-soluble compounds of Veronica pentasepala, Veronica raoulii and Veronica hulkeana were studied and 30 compounds including 15 iridoid glucosides, 12 phenylethanoid glycosides, the acetophenone glucoside pungenin, the mannitol ester hebitol II and mannitol were isolated. Of these, five were previously unknown in the literature: dihydroverminoside and 3,3′,4,4′-tetrahydroxy-α-truxillic acid 6-O-catalpyl diester, named heliosepaloside, as well as three phenylethanoid glycoside esters heliosides D, E and F, all derivatives of aragoside. The esters of cinnamic acid derivatives with iridoid and phenylethanoid glycosides and an unusually high concentration of verminoside were found to be the most distinctive chemotaxonomic characters of the sun hebes. The chemical profiles of the species were compared and used to assess the phylogenetic relationships in the group.     

Suppression of Microbial Metabolic Pathways Inhibits the Generation of the Human Body Odor Component Diacetyl by Staphylococcus spp

Diacetyl (2,3-butanedione) is a key contributor to unpleasant odors emanating from the axillae, feet, and head regions. To investigate the mechanism of diacetyl generation on human skin, resident skin bacteria were tested for the ability to produce diacetyl via metabolism of the main organic acids contained in human sweat. l-Lactate metabolism by Staphylococcus aureus and Staphylococcus epidermidis produced the highest amounts of diacetyl, as measured by high-performance liquid chromatography. Glycyrrhiza glabra root extract (GGR) and α-tocopheryl-l-ascorbate-2-O-phosphate diester potassium salt (EPC-K1), a phosphate diester of α-tocopherol and ascorbic acid, effectively inhibited diacetyl formation without bactericidal effects. Moreover, a metabolic flux analysis revealed that GGR and EPC-K1 suppressed diacetyl formation by inhibiting extracellular bacterial conversion of l-lactate to pyruvate or by altering intracellular metabolic flow into the citrate cycle, respectively, highlighting fundamentally distinct mechanisms by GGR and EPC-K1 to suppress diacetyl formation. These results provide new insight into diacetyl metabolism by human skin bacteria and identify a regulatory mechanism of diacetyl formation that can facilitate the development of effective deodorant agents.     

Two tricyclic sesquiterpenes from Senecio anteuphorbium and Ursinia nana

The aerial parts of Senecio anteuphorbium afforded a new sesquiterpene diester, its structure being elucidated by extensive NMR investigations of t     

Functionalization of hydroxy compounds with nitrilotriacetic acid for technetium-99m chelation: Excretory properties of the radiolabelled chelates

Substituted monoanilides of nitrilotriacetic acid (NTA) have gained much popularity in recent years as an important class of ligands for technetium-99m (^99mTc) radiopharmaceutical preparations used in liver imaging and function studies. We were interested in investigating the properties of the corresponding ester analogues of this important class of ligands and for this study cyclohexanol was selected as a hydroxy component, which on condensation with nitrilotriacetic acid in the presence of acetic anhydride, furnished the monoester, N-cyclohexyloxycarbonylmethyl iminodiacetic acid 4 and the corresponding diester 5. Phenol on similar condensation produced mainly the diester, N, N-di(phenyloxycarbonylmethyl) aminoacetic acid 2, with traces of the corresponding monoester 7. A reinvestigation of the well known condensation reaction of aniline with nitrilotriacetic acid revealed that in addition to the reported monoanilide, N-phenylcarbamoylmethyl imino diacetic acid 3, the corresponding dianilide 6 was also produced in appreciable amount. The ester ligands 2, 4, 5 after ^99mTc chelation exhibited good in vitro and in vivo stabilities. The biodistribution characteristics of these radiolabelled esters and amides were very similar showing thereby that esterification with NTA could be an effective method for converting alcohols to ^99mTc-radiopharmaceuticals without generating any unusual properties because of the ester linkage. Residual radiopharmaceutical concentration after i.v. administration of these amide and ester ^99mTc chelates at 30 min in blood, urine, liver, kidney and intestine were correlated with their lipophilicities and during this correlation it was observed that in addition to lipophilicity the anionic strength of these chelates is also an important determinant in governing their biodistribution. The ester ligand 4 after ^99mTc chelation showed ultrafast hepatobiliary kinetics and was therefore compared in a rabbit model with a standard hepatobiliary radiopharmaceutical ^99mTc-N-(p-butylphenylcarbamoyl methyl) iminodiacetic acid (^99mTc-BIDA) by γ-camera scintigraphy to investigate the potential of the former for clinical studies.     

Structure revision of emiline a pyrrolizidine alkaloid from Emilia flammea

The structure of emiline, a pyrrolizidine alkaloid isolated fromEmilia flammea has been revised from an 11-membered alkaloid to a 12-membered macrocyclic diester containing otonecine.     

Malabaricane derivatives from Pyrethrum santolinoides

The roots of Pyrethrum santolinoides afforded two further representatives of the rare type of malabaricane-triterpenes, a davanone derivative and in addition to known compounds a diester derived from carvotanacetone.     

Phase transitions of alkyl ether analogs of phosphatidylcholine

The phase-transition temperatures of aqueous dispersions of diester, monoether and diether analogs of phosphatidylcholine were determinmed using transparinaric acid as a fluorescent probe. The diether analog of phosphatidylcholine has a higher phase-transition temperature, whilst the monoether analog has a lower phase-transition temperature than their diester counterpart.     

Isolation and structure of mortonol A,a possible biogenetic sesquiterpene precursor of mortonins A,C and D

The structure of mortonol A isolated from Mortonia greggii was established as a benzoate diester of 1α,4β,9β-trihydroxy-dihydroagarofurane-6-one. Its structure and stereochemistry were determined by chemical and spectroscopic means.     

The structure of the type-specific polysaccharide of Pneumococcus type XIX

The structure of the capsular polysaccharide of Type XIX Streptococcus pneumoniae (S-XIX) has been elucidated by ¹H- and ¹³C-n.m.r. spectroscopy. Mild hydrolysis of S-XIX with acid yielded a major oligosaccharide, the repeating unit of S-XIX, which was shown to be O-2-acetamido-2-deoxy-β-d-mannopyranosyl-(1→4)-O-α-d-glucopyranosyl-(1→2)-l-rhamnose 4′′-phosphate. Phosphoric acid forms a diester linkage in the S-XIX molecule, which explains the instability of S-XIX towards acid or alkali. The phosphodiester linkages in S-XIX join HO-1 of α-l-rhamnose and HO-4 of the 2-acetamido-2-deoxy-d-mannopyranosyl residue in the next repeating-unit. Treatment of S-XIX with alkali or alkaline-NaBH₄ produced the repeating units in a lower yield. The proposed structure of S-XIX is

     

Highly efficient solid phase synthesis of oligonucleotide analogs containing phosphorodithioate linkages

A triester method for the synthesis of deoxynucleoside phosphorodithioate dimers is described. The phosphorodithioate linkage is introduced using a new dithiophosphorylating reagent DPSE-SP(S)Cl₂ where DPSE = 2-diphenylmethylsilylethyl. This group is removed quickly using tetra-butylammonium fluoride leading to the quantitative formation of phosphorodithioate diesters uncontaminated with the corresponding phosphorothioates. The utility of this group is demonstrated by the synthesis of a pentadecathymidylic acid, [T(PS₂)T(PO₂)]₇T, which contains alternating phosphorodithioate/phosphate diester internucleotide linkages.     

Chemoenzymatic synthesis of sucrose-containing aromatic polymers.

A chemoenzymatic approach was developed to prepare sucrose-containing aromatic polymers. The protease from Bacillus licheniformis catalyzed the transesterification of sucrose with a diester of terephthalic acid in pyridine to give the mono- and diester products. At 45 degrees C, >70% of sucrose was consumed after 1 day and sucrose diester began to form after 6 days when >95% of sucrose had been converted to sucrose monoester. The final yield of sucrose diester after 20 days was 13.8%. The sucrose monoester was identified as sucrose 1'-terephthalate and the diester products consisted of sucrose 6,1'-diterephthalate and sucrose 6',1'-diterephthalate in a ratio of 2:1. The sucrose diester products were polymerized with ethylene-glycol and ethylene-diamine to give poly(ethylene-terephthalate) and poly(ethylene-terephthalamide), with sucrose contained in the polymer backbone. The polycondensation reactions were carried out in dimethylsulfoxide (DMSO) at 70 degrees C using zinc acetate as a catalyst. The sucrose-containing polyester and polyamide were obtained at 65% yield for 24 h and at 73% yield for 12 h, respectively. End-group analysis of the polymers by (13)C-NMR or (1)H-NMR in DMSO provided a number average molecular weight of 3200 and 4300 Da, respectively. Structural analyses of the polymers were performed with (1)H-NMR, (13)C-NMR, and FTIR. On the basis of (13)C-NMR, acylation of the C1', C6, and C6' hydroxyls were maintained in the polymer backbones.