Stereospecific synthesis of cis-2-alkenylcyclopropane carboxylic acids; A total synthesis of (±)-cis-chrysanthemic acid

A stereospecific route to $\text{cis}$-2,2-dimethyl-3-alkenyl-cyclopropanecarboxylic Acids is illustrated by a total synthesis of (±)-$\text{cis}$-Chrysanthemic Acid (11). The key step consists of an alicyclic Claisen rearrangement of $\text{O}$-silyl enolates derived from appropriately substituted ($\text{Z}$)-4-hexen-6-olides [e.g.(9)].     

Synthesis of β-d-mannopyranosides and regioselective o-alkylation of dibutylstannylene complexes

Alkylation of dibutylstannylene complexes of 3,4,6-tri-$\text{O}$-benzyl-$\text{D}$-mannopyranose, methyl 6-$\text{O}$-trityl-α-$\text{D}$-mannopyranoside and methyl α-$\text{D}$-mannopyranoside gives respectively β-$\text{D}$-mannopyranoside and 3-$\text{O}$-alkyl derivatives with high selectivity.     

13C-NMR spectra of 6-aminohexyl glycosides of O-β-D-galactopyranosyl-2-acetamido-2-deoxy-β-D-glucopyranose

¹³C-NMR spectral data on 6-aminohexyl glycosides of $\text{O}$-β-$\text{D}$-galactopyranosyl-2-acetamido-2-deoxy-β-$\text{D}$-glucopyranose are pr     

The protection of uracil and guanine residues in oligonucleotide synthesis

The protection of uracil and 2-$\text{N}$-acyl guanine residues with 4-$\text{O}$-phenyl [or 4-$\text{O}$-(2,4-dimethylphenyl)] and 6-$\text{O}$-(2-nitrophenyl) groups as in $\text{7a}$ [or $\text{7b}$] and $\text{9}$, respectively, is described. These $\text{O}$-aryl protecting groups, which appear to withstand the usual conditions of oligonucleotide synthesis, may readily be removed by treatment with 2-nitrobenzaldoximate ions.     

Sugar chemistry without protecting groups: a novel regioselective synthesis of 6-O-acyl-D-glucopyranoses and methyl-6-O-acyl-α-D-glucopyranosides

The primary hydroxyl groups of α-$\text{D}$-glucose and methyl-α-$\text{D}$-glucoside were selectively esterified by treating the free sugars with $\text{N}$-acylthiazolidine-2-thiones, thus affording respectively 6-$\text{O}$-acyl-$\text{D}$-glucopyranoses and methyl-6-$\text{O}$-acyl-α-$\text{D}$-glucopyranosides in high yields. This new reaction is compared with our previous synthesis of 1-$\text{O}$-acyl-β-$\text{D}$-glucopyranoses from β-$\text{D}$-glucose and interpreted in terms of anomeric effect.     

The unexpected intramolecular C-arylation of 2-0-benzylated cyclic sugar derivatives: a useful 1,2-cis-C-glycosylation reaction

Upon treatment with tin(IV) chloride, perbenzylated glycofuranosyl acetates such as 3 or 6 undergo an unusual, intramolecular α-$\text{C}$-arylation resulting from the internal Friedel-Crafts alkylation of the 2-$\text{O}$-benzyl substituent.     

Synthesis of lyposaccharide corresponding to fundamental structure of Salmonella-type lipid A

6-O-(2-Deoxy-2-myristoylamino-6-O-myristoyl-β-D-glucopyranosyl)-2-deoxy-2-myristoylamino-3,4-di-O-myristoyl-D-glucopyranose ($\text{2}$) was prepared in a synthetic approach to lipid A which is the active center of bacterial endotoxin.     

Cyanosugars III : The reaction of trimethylsilyl cyanide with keto,epoxy and acetal derivatives of carbohydrates

Reaction of methyl 2-acetamido-4,6-$\text{O}$-benzylidene-2-deoxy-α-$\text{D}$-$\text{ribo}$-hexopyranosid-3-ulose with Me₃SiCN afforded methyl 2-acetamido-4,6-$\text{O}$-benzylidene-3-$\text{C}$-cyano-2-deoxy-3-$\text{O}$-trimethylsilyl-α-$\text{D}$-$\text{allo}$- Reaction of ethyl 4,6-di-$\text{O}$-acetyl-2,3-anhydro-α-$\text{D}$-mannopyranoside with Me₃SiCN gave the corresponding ethyl 4,6-di-$\text{O}$-acetyl-2-$\text{C}$-cyano-2-deoxy-α-$\text{D}$-glucopyranoside. Reaction of methyl 4,6-$\text{O}$-benzylidene-2,3-anhydro-α-$\text{D}$-allopyranoside or methyl 4,6-$\text{O}$-benzylidene-2,3-di-$\text{O}$-tosyl-α-$\text{D}$-glucopyranoside with Me₃SiCN at - 75° or - 50° gave the corresponding methyl 6-$\text{O}$-[(R)-cyano phenyl methyl]-α-$\text{D}$-glyco-pyranosides with high or total regio and stereoselectivity.     

Synthesis with an immobilized enzyme of N-acetyl-9-O-acetyl-neuraminic acid,a sugar reported as a component of embryonic and tumor antigens.

Condensation of 2-acetamido-6-$\text{O}$-acetyl-2-deoxy-D-mannose with pyruvic acid in the presence of immobilized acylneuraminate pyruvate lyase (2.8 units) gave 5-acetamido-9-$\text{O}$-acetyl-3,5-dideoxy-D-$\text{glycero}$-D-$\text{galacto}$-2-nonulopyranos-1-onic acid ($\text{N}$-acetyl-9-$\text{O}$-acetylneuraminic acid) on the 0.3 mmole scale.     

Conformational dependence of pyranoid rings 1,2-cis-fused to dioxolane rings on the configuration of the dioxolane rings in acetylated derivati

X-Ray and ¹H N.M.R. studies on pyranoid rings 1,2-$\text{cis}$-fused to dioxolane rings in acetylated $\text{D}$-gluco- and $\text{D}$--galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the $\text{D}$-gluco but not in the $\text{D}$-galactopyranose series. The crystal structure of 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-(R)--(l-cyano-ethylidene)-α-$\text{D}$-glucopyranose ($\text{1}$) and 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-($\text{R}$)-(1-cyano-ethylidene)-α-$\text{D}$-galactopyranose ($\text{2}$)have been determined by X-ray analysis. Lattice parameters for $\text{1}$ are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for $\text{2}$ are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened ⁴C₁ and that of the dioxolane ring as distorted E₁. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The ¹H N.M.R. spectra of $\text{1}$ and $\text{2}$ and 3,4,6-tri-$\text{O}$-acetyl-1,2-O-(S)- and (R)-ethylidene-α-$\text{D}$-glucopyranose ($\text{5}$ and $\text{7}$), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ($\text{R}$)-ethylidene-α-$\text{D}$-galactopyranose ($\text{6}$ and $\text{8}$), and 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-($\text{S}$)-and ($\text{R}$)-benzylidene-α-$\text{D}$-glucopyranose ($\text{9}$ and $\text{10}$) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the $\text{D}$-gluco series $\text{1}$, $\text{5}$ and $\text{9}$ may be described as flattened ⁴C₁ and that of $\text{7}$ and $\text{10}$ as ²$\text{S}$₅. The major solution conformation of the pyranoid ring in all compounds in the $\text{D}$-galacto series ($\text{2}$,$\text{4}$,$\text{6}$,$\text{8}$) may be described as flattened ⁴$\text{C}$₁.     

Lithiation of 3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)-2'-deoxyuridine: synthesis of 6-substituted 2'-deoxyuridines

Synthesis of 6-substituted 2'-deoxyuridines can be effected by lithiation of 3',5'-$\text{O}$-(tetraisopropyldisiloxane-1,3-diyl)-2'-deoxyuridine with LDA followed by the reaction of its lithio derivative with electrophiles. This method provides a general, regiospecific and simple route to various types of 6-substituted 2'-deoxyuridines which have, so far, been known to be difficult to prepare.     

Total synthesis of slow reacting substances (SRS's): 6-epi-leukotriene C and 6-epi-leukotriene D

6-$\text{Epi}$-leukotrienes C and D (3 and 4) have been synthesized unambiguously via the 5($\text{S}$), 6($\text{R}$)-epoxide (5,6-$\text{cis}$) which is isomeric with leukotriene A. These 6-$\text{epi}$-leukotrienes are less active (especially 4) than leukotrienes C and D (1 and 2) and have not been found in substantial quantity in natural SRS sources.     

Total synthesis of (+--oudemansin

($\text{+}\text{-}$)-Oudemansin has been synthesized starting from $\text{trans}$-cinnamaldehyde by a route involving the stereoselective Zn(BH₄)₂ reduction of β-keto ester.     

New toxic quassinoid glucosides from Simarouba glauca (x-ray analysis)

Two new toxic quassinoid glucosides, 15-$\text{O}$-β-D-glucopyranosyl glaucarubolone 3 and 15-$\text{O}$-β-D-glucopyranosyl glaucarubol 4, have been isolated from $\text{Simarouba glauca}$ seeds. Their structures were deduced from spectral data and that of 3 established by single-crystal X-ray analysis.     

Bioactive marine metabolites IX. Mycalisines A and B,novel nucleosides which inhibit cell division of fertilized starfish eggs,from the marine sponge mycale sp.

Two novel nucleosides, mycalisines A and B, have been isolated from a marine sponge and their structures elucidated as 4-amino-5-cyano-7-(3-$\text{O}$-methyl-5-deoxy-β-D-$\text{erythro}$-pent-4-enofuranosyl)-pyrrolo[2,3-$\text{d}$]pyrimidine and 5-cyano-7-(3-$\text{O}$-methyl-5-deoxy-β-D-$\text{erythro}$-pent-4-enofuranosyl)-pyrrolo[2,3-$\text{d}$]pyrimidine-4-one, respectively. Both compounds inhibit cell division of fertilized starfish eggs.     

An organocopper mediated synthesis of (E)-1,4-di-tert-butylbutatriene.

In the paper a highly stereoselestive route to $\text{trans}$-1,4-di-tert-butylbutatriene $\text{via}$-$\text{t}$-BuCu induced 1,3-substitution in ($\text{Z}$)-$\text{t}$-BuCHC(Br)CCH is described.     

The optical absorption and emission spectra of Cs2NaSmCl6

Optical absorption and emission spectra are reported for single crystals of the cubic elpasolite Cs₂NaSmCl₆. The variable temperature spectra obtained at high resolution are assigned using energies and relative intensities. Transitions from the ground level, ⁶H_{$\text{5}\text{2}$} to cystal fi levels of ⁶H_{$\text{7}\text{2}$-$\text{15}\text{2}$}, ⁶F_{$\text{1}\text{2}$-$\text{11}\text{2}$}, ⁴G_{$\text{5}\text{2}$-$\text{9}\text{2}$}, ⁴F_{$\text{3}\text{2}$,$\text{5}\text{2}$}, ⁴I_{$\text{9}\text{2}$}, and ⁶P_{$\text{3}\text{2}$, $\text{5}\text{2}$} are located and characterized. Intensity calculations are reported for magnetic dipole allowed transitions. The dominance of vibronic intensity in ⁶H_{$\text{5}\text{2}$}→⁶F _{$\text{1}\text{2}$-$\text{9}\text{2}$} and ⁶P_{$\text{3}\text{2}$, $\text{5}\text{2}$} transitions is accounted for qualitatively through the ligand polarization model involving quadrupole metal (Sm³⁺)-ligand (Cl^?) interaction mechanisms. The E_u″(⁶H_{$\text{5}\text{2}$})→E′(⁶H_{$\text{1}\text{2}$}) E_u′(⁶F_{$\text{1}\text{2}$}) no-phonon transition is postulated to be pure electric quadrupole allowed. The ground state magnetic moment is determined to be very small from magnetic circular dichroism (MCD) spectra.This study has led to the assignment of nearly all of the crystal field levels in the visible and IR region for Cs₂NaSmCl₆. A total of 27 such levels were identified, 17 from no-phonon transitions and the rest from vibronic transitions. The magnetic dipole intensity calculated using intermediate coupling O_h wavefunctions along with a crystal field analysis of the splitting pattern was used in the assignment of the levels. Vibronic bands were observed for all transitions and their vibrational symmetries were tentatively assigned. MCD data were used to determine the magnet moment of the ground state.     

Alkaline hydrolysis of 2-(trifluoromethyl)imidazo[4,5-f] and -[4,5-h]quinolines

2-(Trifluoromethyl)imidazo[4,5-$\text{f}$] and -[4,5-$\text{h}$]quinoline have been prepared from 5(6),acetamido-2-(trifluoromethyl)benzimidazole and 7,8-diaminoquinoline respectively. These (trifluoromethyl)- quinolines like 2-(trifluoromethyl)imidazoles but unlike 2-(trifluoromethyl) benzimidazoles, undergo hydrolysis in dilute sodium hydroxide to give ultimately the corresponding imidazo[4,5-$\text{f}$] and -[4,5-$\text{h}$]- quinoline, respectively.     

12-S-CIS conformationally locked retinoids: Thermal and photochemical interconversions leading to new geometric isomers

For 12-$\text{s}$-$\text{cis}$ locked retinal analogues, thermal equilibria are established between 11-$\text{cis}$, 13-$\text{cis}$-1c and 13-$\text{cis}$-2c and between 9-$\text{cis}$, 11-$\text{cis}$, 13-$\text{cis}$-1d and 9-$\text{cis}$, 13-$\text{cis}$-2d; a photoisomerization occurs to transform 2c to $\text{all}$-$\text{trans}$-2a and 2d to 9-$\text{cis}$-2b     

Biosynthesis of psilotin from [2′,3′-13C2,1′-14C,4-3H]phenylalanine studied with 13C-NMR

The 6-phenyl-dihydro-α-pyrone moiety of psilotin is formed from [2′,3′-¹³C₂,1′-¹⁴C,-4-³H]phenylalanine in the plant $\text{Psilotum}$$\text{nudum}$ with retention of all the isotopes.