Stereocontrolled synthesis of clerodin homolog: A Synthetic approach to structure-activity relationships

In order to elucidate the structure-activity relationships of the antifeeding di-terpenes, clerodin homolog $\text{5}$ was stereoselectively synthesized through 18 steps $\text{via}$ a key intermediate $\text{12}$. The perhydrofuro[2,3-b]furan ring in the synthesized homolog was less stable than that of the natural product, and its reactivity on methanolysis and potency of the antifeeding activity were almost the same as those of a 2,6-di-methylphenyl derivative $\text{10}$ which is more sterically restricted than a phenyl derivative $\text{2}$. The findings supported the hypothesis for the relationships on the structure (stereostructure) and activity of biological active substances. The methodology is conceptually termed “Dynamic structure-activity relationships,” and is effective from the standpoint of drug design.     

Synthese von oligosaccharid-determinanten des T-antigens mit amid-spacer zur darstellung synthetischer antigene

The β (1 → 3) -linked disaccharide $\text{1}$$\text{5}$ was synthesized from $\text{D}$-galactose and a $\text{D}$-galactosamine unit with a watersoluble amide spacer. This represents the hapten of T-antigen and, when coupled to a protein, is suitable for use as an artificial antigen. Other O-β-$\text{D}$-galactosylated derivatives of galactosamine were synthesized.     

Reversal of diastereofacial selectivity in the intramolecular michael addition of -α-carbamoyloxy-α,β-unsaturated esters. Synthesis of N-benzoyl-D,L-daunosamine

Contrary to the precedents, 1,3-anti stereoselection was found in the intramolecular Michael addition of ethyl $\text{threo}$,5-carbamoyloxy-4-trialkylsilyloxy-2-hexenoate to culminate in a synthesis of N-benzoyl-$\text{D}$,$\text{L}$-daunosomine. The antiperiplanar effect due to the group at 4-position was revealed to play a major role in the stereoselection in this type of reactions. N-benzoyl-$\text{D}$,$\text{L}$-3-epidaunosamine was also synthesized by 1,2-syn asymmetric induction.     

Stereochemical studies—76 saturated heterocycles—63 : synthesis of cis- and trans-n-methyl- and n-benzyl-4.5- and 5,6-tetramethylenetetrahydro-1,3-oxazines; an x-ray study of n-benzyl-cis-4,5-tetramethylenetetrahydro-1,-3-oxazinium- picrate

- The corresponding $\text{cis}$- and $\text{trans-N}$-methyl- and $\text{N}$-benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines $\text{(5a,b-8a,b)}$were synthesized from $\text{cis}$- and $\text{trans-N}$-methyl and$\text{N}$-benzyl-2- aminomethyl-1-cyclohexanols $\text{1a,b,2a,b}$, from $\text{cis}$- and $\text{trans-N}$-methyl- and $\text{N}$benzyl -2-hydroxymethyl-1-cyclohexylamines$\text{(3a,b,4a,b)}$ by reaction with formaldehyde. The aminoalcohols $\text{1a,2a,3a,b}$and $\text{4a,b}$ were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the $\text{cis}$ isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of $\text{N}$-benzyl-$\text{cis}$-4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate $\text{(7b)}$. determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy.     

1-phenyl-3-(trifluormethansulfonyl)-propadien

For the first time a perfluoroalkanesulfonylallene, the 1-phenyl-3-(trifluoromethanesulfonyl)-propadiene ($\text{5}$) was synthesized. $\text{5}$ is $\text{5}$ reacts already at room temperature with cyclopentadiene to form the adduct $\text{6}$.     

Synthesis of optically active pheromones with an epoxy ring, (+)-disparlure and the saltmarsh caterpillar moth pheromone [(Z,Z)-3,6-cis-1-9,10-epoxyheneicosadiene]

(+)-Disparlure $\text{2}$, and the saltmarsh caterpillar moth pheromone enantiomers $\text{1}$ were synthesized and the stereochemistry of the naturally occurring $\text{1}$ was shown to be 9$\text{S}$, 1O$\text{R}$.     

Synthesis of optically active forms of faranal,the trail pheromone of pharaoh's ant

(3$\text{S}$ 4$\text{R}$)-(+)-Faranal and its antipode were synthesized. The former was comparable in bioactivity with that of the natural pheromone.     

A synthesis of the aromatic segment of rifamycin s

The aromatic segment $\text{15}$ of rifamycin S ($\text{1}$) was synthesized from the cyclohexadienone $\text{2}$ or $\text{ii}$ in high overall yield.     

Synthesis and some structural data of nylon 18

The new polyamide nylon 18 was synthesized, mainly to investigate whether a rather large number of methylene groups in the monomeric unit might change the chain packing in comparison with that of lower even nylons. By X-ray diffraction measurements on a mono-oriented fibre, the following crystallographic parameters were found: $\text{a = 4.76}\text{A}\text{?}$; $\text{b = 9.52}\text{A}\text{?}$; $\text{c = 46.9}\text{A}\text{?}$ (fibre axis); γ = 120°. A γ-type packing for the chains was found, similar to that shown by other polyamides of the series.     

Conversion of 6-protoilludene into illudin-M and -S by omphalotusolearius

Deuterium labeled $\text{dl}$-6-protoilludene ($\text{7}$) was synthesized and fed to the illudin-producing fungus $\text{Omphalotus}$$\text{olearius}$ (ATCC 11719). The hydrocarbon ($\text{7}$) was incorporated into illudin-M ($\text{2}$) and -S ($\text{3}$).     

Application of the α-alkynone cyclization : synthesis of rac-modhephene

Using the thermal α-alkynone cyclization $\text{8}$ → $\text{9}$ as the key step, modhephene $\text{1}$, a sesquiterpene with a [3.3.3]-propellane skeleton was synthesized.     

Syntheses of (1,1-dihydroperfluoroalkyl)aryliodonium triflates and their analogues

(1,l-Dihydroperfluoroalkyl)phenyl- and -$\text{p}$-fluorophenyliodonium triflates $\text{2}$ and $\text{3}$ were synthesized by the reaction of l-bis(trifluoroacetoxy)iodo-1,l-dihydroperfluoroalkanes $\text{1}$ with triflic acid and benzene or fluorobenzene in 1,1,2-trichlorotrifluoroethane. The use of fluorosulfonic acid and sulfuric acid instead of triflic acid afforded (1,l-dihydroperfluoroalkyl) phenyliodonium fluorosulfonate $\text{4}$ and sulfate $\text{5}$, respectively. Similarly, (1,1,ω-trihydroperfluoroalkyl)phenyliodonium triflate $\text{7}$ and 1,1,5,5-tetrahydroperfluoropentane-l,5-bisphenyliodonium triflate $\text{9}$ were synthesized.     

Chemical synthesis of the 5-́half molecule of E.coli tRNA2GLY

A tritriacontanucleotide which has the sequence of the 5$\text{-}\text{?}$half molecule of E.coli glycine tRNA₂, was synthesized by the phosphotriester method involving p-anisidate protection for the 3$\text{-}\text{?}$phosphate ends. Di- and trinucleotide units were prepared from 5$\text{-}\text{?}$dimethoxytrityl-2$\text{-}\text{?}$O-tetrahydrofuranyl-3?-O-(o-chlorophenyl)phosphoryl derivatives of uridine, N-benzoylcytidine, N-benzolyadenosine and N-iso-butyrylguanosine by condensation with 3$\text{,}\text{?}$5$\text{-}\text{?}$unprotected nucleosides followed by phosphorylation to give 3$\text{-}\text{?}$phosphodiester blocks. The 3$\text{-}\text{?}$terminal dimers and trimers were synthesized by using 3$\text{-}\text{?}$(o- chlorophenyl)phosphoro-p-anisidates instead of 3?,5?-unprotected nucleosides. The 3?-phosphodiesters of oligonucleotides with a chain length of larger than 5 were obtained by removal of the 3?-phosphoro-p-anisidate with isoamyl nitrite. The 5$\text{-}\text{?}$dimethoxytrityl group was removed by treatment with zinc bromide under anhydrous conditions. Fragments were designed to use common dimer blocks and to reduce the step for 5$\text{-}\text{?}$deblocking of larger fragments. Finally a 3$\text{-}\text{?}$phosphodiester block with a chain length of 20 was condensed with a 5$\text{-}\text{?}$OH component (tridecanucleotide). The fully protected 33 mer was deblocked and purified by chromatography. The structural integrity of the product was confirmed by mobility shift analysis and complete digestion with RNase T2.     

Ene reaction of α-thiocarbocation: Simple synthesis of E,E-2,4-alkadienoic esters from 1-alkenes

Pummerer reaction intermediate $\text{2}$ of α-methylsulfinylacetate ($\text{1}$) has been found to react with 1-alkenes to afford ene adducts $\text{3}$. E,E-2,4-decadienoic ester ($\text{5}$) was synthesized from the adduct $\text{3}$ (n=5).     

The synthesis of l-α-aminoadipyl-l-cysteinyl-d-3,4-didehydrovaline,a potent inhibitor of isopenicillin synthetase

The title peptide ($\text{1}$) has been synthesized and incubated with an active cell-free extract of $\text{Cephalosporium}$$\text{acremonium}$, no conversion to active antibiotics was observed; however on co-incubation with the Arnstein tripeptide (ACV) ($\text{2}$), strong inhibition of the conversion of ACV to isopenicillin N was observed.     

Synthesis and transformations of a 20-deethyl 3-oxo vincadifformine.

A 20-deethyl 3-oxo vincadifformine $\text{3}$ was synthesized via condensation of 2-hydroxy tryptamine with synthon $\text{9}$. It was further alkylated to the oxo-pseudovincadifformine $\text{2}$. The given relative configurations remain hypothetical.     

Synthetic studies toward marine toxic polyethers (3) stereocontrol for segment-A1 of okadaic acid by means of oxymercuration and epoxydation

Segment-A₁ of okadale acid was synthesized from glucose via an acyclic stereocontrol for C-2 by means of oxymercuration. The stereochemistry was proven by comparison with $\text{S}$ and $\text{R}$ epoxides which were synthesized selectively by chelational and stereoelectronic effects, respectively.     

A model study for the biomimetic-type synthesis of rifamycin S

Acid treatment of the hydroperoxide $\text{5}$ yielded the enol ether $\text{9}$. Hydrogenation of $\text{9}$ gave the dihydro derivative, the structure of which was established by comparison with the substance synthesized by a different route.     

π...π-interactions of flavins,-II. [3.3](3,10)Isoalloxazinophane and quinhydrone-like flavin interactions

To study flavin-flavin interactions [3.3](3,10)isoalloxazinophane was synthesized and its structure determined as $\text{4}$. Electron spectra including charge-transfer absorptions of semi-reduced states are reported for $\text{4}$ in comparison with the mono-bridged bis-flavin analogue $\text{3}$.     

Stereoselective synthesis of the optically active functionalized 1,3,5-all-anti-triol

The optically active 1,3,5-$\text{all}$-$\text{anti}$-triol $\text{20}$ was synthesized starting from ($\text{S}$)-(-)-malic acid with complete stereoselection, based on the stereoselective reduction of cyclic β-keto acetal and successive transthioacetalization.