Assignment Of Absolute Stereochemistry Research Articles

Assignment of absolute stereochemistry to an insect pheromone by chiral amplification

Chiral amplification, a new strategy for determining the absolute configuration of difficultly available natural secondary alcohols or analogous amines, is described. Using this technique, the R configuration can be assigned to both components of the male sex pheromone emitted by the longhorn beetle, Anaglyptus subfasciatus. The application of this approach to fourteen alcohols and four amines illustrates its scope and limitations.

Diastereoselectivity and assignment of absolute stereochemistry in the aza-Diels–Alder reaction of a sulfonylimino acetate with 1-methoxy-3-trimethylsilyloxybuta-1,3-diene

N-[(1R)-(–)-camphor-10-ylsulfonyl]imine 1b generated in situ from the corresponding brominated glycinate 4b reacts with Danishefsky's diene under thermal conditions to give a high yield of diastereoisomeric Diels–Alder adducts 7b and 6b in a 2.04 : 1 ratio. Under Lewis acid catalysis at –78 °C the diastereoselectivity improves slightly to 2.30 : 1 using titanium tetraisopropoxide. However, the sense of asymmetric induction is reversed when using diethylaluminium chloride as the catalyst. Determination of the absolute stereochemistry of the adducts 6b and 7b was achieved by comparison with pipecolic acid derivatives 10b and 12b and showed that 7b had the (2R)-configuration at the newly formed chiral centre and 6b the (2S)-configuration.

ChemInform Abstract: Total Synthesis of the Pollen‐Growth Inhibitor (‐)‐Emeniveol (I). Assignment of Absolute Stereochemistry.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Configurational analysis of new furanosesquiterpenes from Dysidea herbacea. Assignment of absolute stereochemistry.

Two new marine furanoterpenes (+)-(4a S, 6 R,8a S)-4,4,7-trimethyl-4,4a,5,6,8,8a,9-hexahydronaphtho[2,3- b]furan-6-yl acetate ( 1) and (+)-(4a S,7 R,8a S)-6,9,9-trimethyl-4,4a,7,8,8a,9-hexahydronaphthol[2,3 b]furan-7-yl acetate ( 2), were isolated sample of Dysidea herbacea collected from Harrier Reef on the Great Barrier Reef, Australlia. The enantiomer of 1, (−)-(4a R,6 S,8a R)-4,4,7–trimethyl– 4,4a,5,6,8,8a,9–hexahydronaptho[2.3–b]furan–6–yl acetate (17) was found in another sample of D. herbacea collected nearby from Norman Reef. The structures were determined by spectroscopic methods, in particular 2D NMR, and the absolute configurations of the parent rings of 1 and 2 defined by chemical correlation and application of Kakisawa's of the Mosher ester method. Compounds 1 and 2 are diastereomers of acetates 5 and 6, reported earlier from D. herbacea, but have opposite configuration with respect to the ring junctions. These results and others suggest D. herbacea, may possess a dual capacity for antipodal cyclization pathways from a common achiral terpenoid precursor.

Determination of the absolute configuration of the glycerol component in poly(glycosylglycerolphosphates) by GLC-MS

The identification of an increasing number of teichoic acid-like capsular polysaccharide structures containing glycerol phosphate linkages (see, for example, refs l-141, has necessitated the development of accurate and versatile methods for the determination of the absolute configuration of the chiral glycerol components. Only in a few instances has the assignment of the stereochemistry of 0-glycosyl glycerol, phosphorylated at one of the primary hydroxymethyl groups, within this type of polymer been reported 12-15 On the other hand, the stereochemistry of the . teichoic acids in the cell walls and membranes of gram-positive bacteria appears to be well established16,i7. Assignment of the stereochemistry of the glycerol residue in poly(glycosylglycerol phosphates) may be achieved by release of the chiral glycerol component, followed by its conversion to an appropriate derivative, and assignment of absolute stereochemistry by comparison with standards of known chirality by means of spectroscopic CORD, CD, or NMR), chromatographic or enzymic methods18,i9. In the case of polymers joined by + l)-glycerol-(3 + phosphodiester linkages, depolymerization can be accomplished with aqueous HF to afford a 1-0-glycosylated glycerol fragment. Configurational analysis is then possible by comparison of the chromatographic properties with standards of known absolute configuration2’ or by stereospecific enzymic assay following oxidation to the corresponding chiral glyceric acid . 21 More recen tl y a method based on the measurement of the chiroptical properties of 2,3-di-0-benzyl-sn-glycerol obtained from 1-0-glycosyl-sn-glycerols has been describedz2. When the teichoic acid contains 2-O-substituted glycerol phosphate linkages,

Total synthesis of the pollen-growth inhibitor (−)-emeniveol. Assignment of absolute stereochemistry

The total synthesis of emeniveol, a pollen growth inhibitor, is described and its absolute stereochemistry was determined using (+)-Wieland-Miescher ketone as the starting material.

Two New Sesterterpenes from a South China Sea Sponge

Two new scalarane derivatives, phyllactones F and G, have been isolated from the sponge Phyllospongia foliascens. Compounds 1 and 2 are anomers whose structures were determined on the basis of spectral data. The absolute stereochemistry of phyllactone B [6] has been established using Moshet's method, and this permitted verification of the assignments of absolute stereochemistry for all scalarane sesterterpenes isolated from the Chinese sponge P. foliascens

Spongiaquinone Revisited: Structural and Stereochemical Studies on Marine Sesquiterpene/Quinones From a Southern Australian Marine Sponge, Spongia sp.

A chemical investigation of a large purple sponge, Spongia sp., from the Great Australian Bight, resulted in the isolation of a new sesquiterpene/quinone (8), together with the known compounds dehydrocyclospongiaquinone-1 (4) and spongiaquinone (2). The last compound was also isolated as the potassium salt (9), this being the first recorded account of a naturally occurring marine sesquiterpene/quinone salt. The structure for (8) was assigned by detailed spectroscopic analysis. A re-investigation into the stereostructure of spongiaquinone (2) resulted in the first unambiguous assignment of absolute stereochemistry, and uncovered the peculiar chiroptical properties of spongiaquinone (2) and its potassium salt (9).

Gilvocarcin M synthesis wins praise for elegance

Total syntheses of natural products are not that uncommon, but organic chemists seem to be uncommonly impressed by the six-step total synthesis and absolute stereochemical assignment of gilvocarcin...

Total synthesis and absolute stereochemical assignment of gilvocarcin M.

Total synthesis and absolute stereochemical assignment of gilvocarcin M.

The Luffarins (A-Z), Novel Terpenes From an Australian Marine Sponge, Luffariella geometrica

A marine sponge, Luffariella geometrica Kirkpatrick, collected from the southern Australian coastal waters of the Great Australian Bight, has been found to contain 14 new bicyclic sesterterpenes, luffarin-A (14), -B (15), -C (16), -D (17), -E (18), -F (19), -G (20), -H (21), -I (22), -J (23), -K (24), -L (25), -M (26) and -N (27), a new bicyclic bisnorsesterterpene, luffarin-O (30), a new monocyclic sesterterpene, luffarin-P (32), six new acyclic sesterterpenes, luffarin-Q (35), -R (36), -S (37), -T (38), -U (39) and -V (40), two new diterpenes, luffarin-W (41) and -X (44), and two new bisnorditerpenes luffarin-Y (45) and -Z (46). These novel marine metabolites have been assigned structures, including stereochemistry, on the basis of detailed spectroscopic analysis, chemical correlation, derivatization, and biosynthetic considerations. Studies directed at the absolute stereochemistry of the luffarins have also permitted assignment of absolute stereochemistry to the known marine natural products (E)-neomanoalide (3), (Z)-neomanoalide (4) and dehydroambliol-A (47).

Assignment of absolute stereochemistry of aminopolyols by the bichromophoric exciton chirality method

A general procedure for assigning relative and absolute configurations to multiple stereocentres in acyclic aminopolyols, and its microgram-scale application to an aminobacteriohopanetriol is presented.

An unusual oxidative cyclization. A synthesis and absolute stereochemical assignment of (-)-rocaglamide

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn unusual oxidative cyclization. A synthesis and absolute stereochemical assignment of (-)-rocaglamideBarry M. Trost, Paul D. Greenspan, Bingwei V. Yang, and Mark G. SaulnierCite this: J. Am. Chem. Soc. 1990, 112, 24, 9022–9024Publication Date (Print):November 1, 1990Publication History Published online1 May 2002Published inissue 1 November 1990https://doi.org/10.1021/ja00180a081RIGHTS & PERMISSIONSArticle Views1475Altmetric-Citations82LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (386 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

ChemInform Abstract: The Effect of Acetylene Substituents on a Pd(II)‐Catalyzed Cycloisomerization. Total Synthesis of (‐)‐Sterepolide and Assignment of Absolute Stereochemistry.

AbstractA novel asym.

Synthesis, resolution and absolute stereochemical assignment of C1-oxygenated allylsilanes and C3-oxygenated vinylsilanes

(R)-O-acetyl mandelic acid has been utilized for the development of a procedure for resolution and absolute stereochemical assignment of C1-oxygenated E-crotylsilanes 1a-c. The procedure is enhanced further by an efficient boron trifluoride etherate catalyzed allylic transposition which generates E-vinylsilanes. Subsequent resolution and hydrolysis produced the vinylsilanes 6a, b and d in optically active form. The published method of Trost and cowoarkers has allowed for the assignment of absolute stereochemistry.

A new synthesis resolution and in vitro activities of (R)- and (S)-β-Phenyl-Gaba

β-Phenyl-GABA (2) was resolved by separation by crystallization and/or h.p.l.c. of the diastereoisomeric (R)-(-)-pantolactone esters of the N-phthalimido protected β-phenyl-GABA. The absolute stereochemical assignments obtained from chiroptical studies of the enantiomers(8a) and(8b) and an X-ray crystallographic study of the diastereoisomer(7a) were supported by the activities of the enantiomers(8a) and(8b) in binding and electrophysiological studies. Details of synthesis, binding, electrophysiological, chiroptical and X-ray crystallographic studies are reported.

Enantiomeric Relationships and Anthelmintic Activity of Dysinin Derivatives from Dysidea Marine Sponges

This report will consider the absolute stereochemical assignments of these and other dysinin sesquiterpenes along with an analysis of the separate occurrence of members of the two enantiometric series. Also disclosed will be the results of anthelmintic evaluation of dysinins (−)-4, (−)-5, (−)-6, and (+)-7

The Effect of Acetylene Substituents on a PdII‐Catalyzed Cycloisomerization. Total Synthesis of (–)‐Sterepolide and Assignment of Absolute Stereochemistry

The Effect of Acetylene Substituents on a Pd^II‐Catalyzed Cycloisomerization. Total Synthesis of (–)‐Sterepolide and Assignment of Absolute Stereochemistry

The total syntheses of the isodityrosine-derived cyclic tripeptides OF4949-III and K-13. Determination of the absolute configuration of K-13

The asymmetric syntheses of the two cyclic tripeptides OF4949-111 and K-13 have been completed. The absolute stereochemical assignment of the former compound has been confirmed, while the absolute configuration of the latter has been established for the first time. The expedient bidirectional synthesis of a fully differentiated isodityrosine, a common

Stereochemical studies on marine cyclic peroxides : an unequivocal alignment of absolute stereochemistry by asymmetric synthesis

Absolute stereochemical assignments for norterpene cyclic peroxides from marine sponges, previously determined by application of the Horeau procedure of asymmetric esterification, have been independently confirmed by degradation and asymmetric synthesis.