Reductive coupling of α,β-enones I: Reduction of methyl-vinyl ketone and mesityl oxide.

Reductive coupling of methyl-vinyl ketone with TiCl₄-Mg gives pinacol $\text{1}$ (25%). According to the reducing agents, mesityl oxide yields 2,4,5,7-tetramethyl-octa-2,4,6-triene $\text{3}$ (with 4TiCl₃-LialH₄), triene $\text{3}$ or 2,4,5,7-tetramethyl-octa-2,6-dien-4,5-diol $\text{5}$ (with TiCl₄-Mg), pinacol $\text{5}$ (with VCl₃-Mg), and 2-acetyl-1,3,3,4,4-pentamethyl-cyclopentane $\text{7}$ (with CrCl₃-Mg or FeCl₃-Mg or ZrCl₄ or ZrCl₄-Mg) as major products.     

N-halogeno-compounds. Part 9 [1]. Azoxy- and azo-arenes derived from 4-(dichloroamino)tetrafluoropyridine; crystal structure of trans-2,3,5,6-tetrafluoro-4-(2,4,6-trimethylphenyl-onn-azoxy)pyridine

The nitrosoarenes ArNO (Ar = C₆H₅, 2-MeC₆H₄, 2,4,6- Me₃C₆H₂ and C₆F₅) have been condensed with 4-(dichloroamino)- tetrafluoropyridine to provide the azoxy-compounds py_FN$\text{N}\text{+}$($\text{N}\text{-}$)Ar (py_F = 2,3,5,6-tetrafluoro-4-pyridyl); de-oxygenation of the first three with triphenylphosphine or triethyl phosphite gave the corresponding azo-compounds, and the reverse reaction was achieved in the case of py_FNNC₆H₂Me₃-2,4,6 using peroxytrifluoroacetic acid. Thermolysis of 4-azidotetrafluoropyridine in the presence of pentafluoronitrosobenzene provided the perfluorinated azoxy-compound py_FN$\text{N}\text{+}$($\text{O}\text{-}$)C₆F₅. X-Ray methods have been used to determine the molecular geometry of py_FN$\text{N}\text{+}$($\text{O}\text{-}$)C₆H₂Me₃-2,4,6.     

Stereoselektive c-glycosidsynthese durch titan-(iv)-katalysierte addition von silylenolethern an 2-acyloxy-3-keto-glycale

C-Glycosides are stereoselectively formed by the titan-(IV)-catalysed addition of silyl enolethers $\text{2}$ to 2,4,6-tri-O-acyl-1-deoxy-D-erythro-hex-1-enopyran-3-uloses $\text{1}$ followed by elimination of the 4-acyloxy substituent. Cyclohexenyl silylether $\text{2a}$ reacts with 2-acetoxy-3-keto-glycal derivative $\text{la}$ forming only one product $\text{3a}$. Thus, the reaction seems to be diastereospecific with respect to both new chiral centers of the product.     

Syntheses of enantiomeric dihydropyrans through stereocontrolled intramolecular cycloaddition

Reaction of the cyclic 1, 3-dicarboxylic acid derivatives ($\text{1}$), ($\text{2}$) and ($\text{3}$) with (R)- or (S)-citronellal ($\text{4}$/$\text{5}$) gives the enantiomeric tricyclic dihydropyrans ($\text{10}$), ($\text{11}$), ($\text{12}$) and ($\text{13}$), probably via a 100% stereocontrolled intramolecular cycloaddition.     

A reinvestigation of the structures of acomonine,iliensine, 14-dehydroiliensine,and 14-benzoyliliensine

The novel structures assigned by Yunusov et al to the C₁₉-diterpenoid alkaloids, acomonine ($\text{1}$), iliensine ($\text{2}$), 14-dehydroiliensine ($\text{3}$), and 14-bensoyliliensine ($\text{4}$) have been found to be in error. We have demonstrated that these alkaloids are identical with the well-known alkaloids, delsoline ($\text{5}$), delcosine ($\text{6}$), 14-dehydrodeloosine ($\text{7}$), and 14-benzoyldelcosine ($\text{8}$), respectively.     

The cybrodins: new seco-illudalanes from the bird's nest fungus cyathus bulleri brodie.

The structures of the $\text{seco}$-illudalane sesquiterpenoids cybrodol $\text{2}$), isocybrodol ($\text{3}$), cybrodic acid ($\text{6}$), cybrodal ($\text{4}$), and trisnorcybrodolide ($\text{5}$), are presented. These are the first $\text{seco}$-illudalanes to be reported.     

Five new steroidal glycosides,pregnedioside-A, -B,and their three monoacetates,from an Okinawan soft coral of Alcyonium sp.

Five new pregnene-type steroidal glycosides, named pregnedioside -a ($\text{1}$), 4′-O-acetyl-pregnedioside-a ($\text{2}$), 3′-O-acetyl-pregnedioside-a ($\text{3}$), pregnedioside-b ($\text{5}$), and 4′-O-acetyl-pregnedioside-b ($\text{6}$), were isolated from an Okinawan soft coral of Alcyonium sp. and their structures were elucidated. These are rare examples of steroidal gylcosides from soft coral.     

A new strategy for the protection of deoxyguanosine during oligonucleotide synthesis

The protection of the 6-oxo group of deoxyguanosine with the 2-trimethylsilylethyl ($\text{2}$), phenylthioethyl ($\text{3}$), 4-nitrophenylthioethyl ($\text{4}$), 4-nintrophenethyl ($\text{5}$), and cyanoethyl ($\text{6}$) groups is described. Each protecting group is introduced in good yield and is cleaved under mild conditions. Compatibility with the various approaches to oligonucleotide synthesis is discussed.     

A convenient synthesis of 1,3-dimethyl(5h,7h)imidazo(4,5-dpyrimidine-2,4,6-trithione and its unusual character

1,3-Diemthyl(5H,7H)imidazo(4,5-$\text{d}$pyrimidine-2,4,6-trithione ($\text{1}$) was synthesized by the reaction of carbon disulfide with 1,3-dimethyl-4-cyano-5-aminoimidazolidine-2-thione ($\text{3}$) which was produced by reacting trimethylsilyl cyanide with methyl isothiocyanate followed by methanolysis. An unusual reversible formation of the dimethylamine salt of $\text{1}$ is also described.     

Photocycloaddition reactions of the first stable thioaldehyde: 2,4,6-tri(tert-butyl)thiobenzaldehyde with substituted allenes

Irradiation of 2,4,6-tri-(tert,-butyl)thiobenzaldehyde $\text{1}$ with some alkoxy-, alkylthio-, and phenyl-allenes $\text{2}$$\text{a}$-$\text{i}$ gave one stereoisomer of a (2+2)-cycloadduct, viz. thietane $\text{3}$ in high yields (75–95%). Ringclosure is in agreement with MNDO-calculations.     

Phospha-S-triazines. VIII. Chloro-substituted diphospha-S-triazines

1,3-Bis(phenylchlorophospha)-5-perfluoroalkyl-2,4,6- triazine and the corresponding perfluoroalkylether analogue were synthesized by interaction of equimolar amounts of the respective amidines and imido-diphenyl-diphosphinic acid pentachloride. With additional quantities of amidine, 1,3-bis(phenylperfluoro-$\text{n}$-octanoylamidinophospha)-5-perfluoro- $\text{n}$-heptyl-2,4,6-triazine was obtained. The replacement of the chloro- by azido-groups in 1,3-bis(phenylchlorophospha)-5- perfluoro-$\text{n}$-heptyl-2,4,6-triazine proceeded readily. The mass spectral breakdown patterns of the chloro- and the amidino- substituted compounds were directly comparable to those of the bis(diphenylphospha)-s-triazines.     

Pyrolysis of homoadamant-3-ene

Pyrolysis of homoadamant-3-ene ($\text{5}$), generated from 1-adamantylcarbene ($\text{7}$), leads to the same three olefins ($\text{2}$, $\text{3}$, and $\text{4}$) that are produced from pyrolysis of 3-homoadamantyl acetate ($\text{1}$).     

Complexes of carbonyl compounds with RnAlX3-n compounds: III. The stoichiometry of complexes of ketones with aluminium trichloride

Acetophenone and p-methylacetophenone complex with aluminium trichloride; $\text{1}\text{1}$ and $\text{1}\text{2}$ complexes are formed in equilibrium in benzene solution. A 6-membered ring structure is proposed for the $\text{1}\text{2}$ complex.     

Synthesis of bicyclo[6.2.2] bridgehead dienes

Bicyclo[6.2.2]dodecadienes ($\text{2}$), ($\text{3a}$), and ($\text{3b}$) having two bridgehead double bonds were synthesized by the pyrolysis of the acetate ($\text{1}$).     

Stekeospecific transformation of D-sugar to L-sugar in complex aminoglycoside. Synthesis of a kanamycin B analog having 2,6-diamino-2,4,6-trideoxy-L-arabino-hexopyranose

A 4′-ene derivative of kanamycin B ($\text{4}$) was derived from the epoxide ($\text{1}$) by oxidative elimination of the 4′-phenylseleno group into the allylic alcohol ($\text{3}$). The title compound, 0-(2,6-diamino-2,4,6-trideoxy-β-L-arabino-hexopyranosyl)-(1→4)-0-[3-amino-3-deoxy-α-D-glucopyranosyl-(1→6)]-2-deoxystreptamine ($\text{6}$) was obtained from $\text{4}$ by stereospecific hydrogenation followed by removal of the masking groups, changing the D-sugar moiety of the 4-0-glycoside portion into an L-sugar.     

Methyl 3-0-benzyl-2,4,6-trideoxy-6-iodo-α-d-erythro-hexopyranoside,a chiral synthon for the synthesis of inhibitors of HMG-CoA reductase

Methyl 3-0-benzyl-2,4,6-trideoxy-6-iodo-α-D-$\text{erythro}$-hexopyranoside $\text{2}$ was prepared from D-glucose and demonstrated to have potential utility as a chiral synthon for the elaboration of HMG-CoA reductase inhibitors.     

The total synthesis of i-oxygenated eudesmanolides

A route towards I-oxygenated eudesmanolides, via a (2+2) photocycloaddition reaction for constructing the decalin framework is described. The following natural substances have been synthesized. (=)-dihydroreynosin ($\text{1}$), (±)-1- oxo-dihydronmagnolialide ($\text{2}$), (±)-maritimin ($\text{3}$), (±)-dihydromagnolialide ($\text{4}$), (±)-magnolialide ($\text{5}$), (±)-dihydrosantamarine ($\text{6}$). Also a synthesis of (±)--santonin ($\text{7}$) is presented.     

Electron exchange chemiluminescence from a sterically stabilized cyclobutadiene-1,2-dioxetane

The rather stable 1,2-dioxetanes ($\text{2}$) and ($\text{3}$), derived from the sterically stabilized cyclobutadiene ($\text{1}$), exhibit distinct enhanced chemiluminescence behavior, namely energy transfer chemiluminescence (ETC) for ($\text{2}$) and electron exchange chemiluminescence (EEC) for ($\text{3}$).     

[4+2]cycloaddition reactions of triarylphosphaalkene

Cycloaddition reactions of mesityl(diphenyliiifithylene)phosphine ($\text{1}$) were Investigated. With several dienes, no Diels-Alder reactions were oEserved. With azides, diphenyidiazomethane and 2,4,6-trimethylbenzonitrile oxide, the corresponding cycloadducts ($\text{4}$$\text{12}$$\text{17}$$\text{12}$were obtained. In the case of phenyl azide, a competing Staudinger reaction occurred leading to $\text{3}$.     

Singlet oxygenation of cis,cis-1,5-cyclooctadiene: a convenient synthetic entry into 5,8-difunctionalized oxygen derivatives of 1,3-cyclooctadiene

The 6-hydroperoxy-1,4-cyclooctadiene ($\text{2}$), which is formed in the photosensitized oxygenation of 1,5-cyclooctadiene ($\text{1}$), affords on further singlet oxygenation 5,8-dihydroperoxy-1,3-cyclooctadiene ($\text{3}$), which via triphenylphosphine reduction leads to $\text{cis}$-5,8-dihydroxy-1,3-cyclooctadiene ($\text{4}$) and subsequent pyridinium chlorochromate oxidation to 1,3-cyclooctadien-5,8-dione ($\text{8}$).