Completely stereoselective synthesis of all four stereoisomeric 1-carbamoyloxy-1,3-alkadienes via anti-diastereoselective homoaldol reaction from aldehydes and a single carbon-three-unit

Lithiation of both ($\text{Z}$)- and ($\text{E}$)-3-trimethylsilyl-2-propenyl $\text{N}$,$\text{N}$-diisopropyl carbamate 2 affords the (2$\text{E}$) -lithium compound 3. Aluminium- or titanium-mediated addition to aldehydes, 4 gives (1$\text{E}$)-(3$\text{R}$*4$\text{S}$*)-enol carbamates 7. A stereospecific Peterson elimination (borontriflouride- or base-mediated) introduces the second double bond either with (3$\text{E}$)- or with (3$\text{Z}$)-configuration. So just by reagent selection for each of the two steps, (1$\text{E}$,3$\text{E}$)-, (1$\text{E}$,3$\text{Z}$)-, (1$\text{Z}$,3$\text{E}$)-, or (1$\text{Z}$,3$\text{Z}$)- dienes 8 - 11, respectively, are prepared with stereoselectivities up to > 99.7%     

Nucleosides-126: Selective methylation of the C-nucleoside, ψ-isocytidine and its 2$́-deoxy analog. Synthesis of 1-methyl, 3-methyl and 4-o-methyl derivatives

Methods were developed to prepare 1 -methyl-, 3-methyl- and 4-0-methyl-ψ-isocytidine by selective methylation.3$\text{,}\text{?}$5$\text{-}\text{?}$O-Tetraisopropyldisiloxanyl-ψ isocytidine (8) was trimethylsilylated and then treated with MeI and, after deprotection, 1 -methyl-ψ isocytidine (6) was obtained. The 2$\text{-}\text{?}$deoxy analog (7) was also prepared in a similar manner from the 2$\text{-}\text{?}$deoxy analog (10) of 8. Treatment of 8 with CH₂N₂ afforded the 3-methyl-ψ-isocytidine derivative (19) as the major product. Methylation with diazomethane also occurred mainly on N3 of the 2$\text{-}\text{?}$deoxy analog 10 to form 20. Removal of the 3$\text{,}\text{?}$ 5$\text{-}\text{?}$O-protecting group from 19 and 20 afforded 3-methyl-ψ-isocytidine (14) and its 2-deoxy analog (15), respectively. 2-N-Acetyl- 3$\text{,}\text{?}$5$\text{-}\text{?}$O-tetraisopropyldisiloxanyl-ψ-isocytidine (24), on the other hand, gave the 4-O-methyl derivative (25) as the major product upon CH₂N₂ treatment. Subsequent deprotection of 25 afforded 4-O-methyl-ψ-isocytidine (29). aiv51b1p33b     

Electronic spectra of 12-S-CIS conformationally locked retinals

The electronic absorption spectra of the four new 12-$\text{s}$-$\text{cis}$-locked retinals (1a–1d) bearing 7-$\text{trans}$, 11-$\text{trans}$ double bond geometries are described and compared with those of analogous 7-$\text{trans}$, 11-$\text{cis}$-geometries (1e–1h) and parent retinals (2a-h).     

o-quinone methides 2. Stereoselectivity in cycloaddition reactions of o-quinone methides with vinyl ethers

Cycloaddition reactions between vinyl ethers 3 and $\text{o}$-quinone methides 2, thermally generated from 2-hydroxybenzyl alcohols 1, have been studied. The structure and conformational preferences of the 4-substituted 2-ethoxy-(2,3)-dihydro-2$\text{H}$-benzopyrans 4–9 obtained, which show new interesting features, are discussed together with competitive kinetic data. The cycloaddition process is concerted and involves $\text{o}$-quinone methides in the $\text{E}$-configuration. The OEt-$\text{endo}$ transition state seems to be preferred with ethyl vinyl ether and $\text{Z}$-1-propenyl ethyl ether, whereas with $\text{E}$-1-propenyl ethyl ether the stereoselectivity of the cycloaddition process depends on substituents on the methylene group of the starting alcohol 1. These results are discussed in terms of $\text{endo}$ and $\text{exo}$ preference of the propenyl ether methyl group.     

Acyclic stereoselection. 35. Effect of cation on diastereofacial selectivity in aldol reactions of a chiral α-silyloxy ketone.

By an appropriate choice of cation, three of the four possible aldols from the reactions of the chiral α-silyloxy ketone 1 with aldehydes may be obtained. The $\text{Z}$, lithium enolate provides 6, the $\text{Z}$, boron enolate gives 7, and the $\text{E}$ magnesium enolate affords 8.     

A synthetic approach to (+)-aldosterone and its relatives (2)- a stereoselective synthesis of (+)-trans-4,5-(4-methoxybenzo)- 1β , 7aβ - ( 2α-methoxymethyl- 5 -oxofuro) hydrindane

A stereoselectivity in an intramolecular cycloaddition of the olefinic $\text{o}$-quinodimethanes 13 and 23 generated $\text{in}$$\text{situ}$ from the thermolysis of optically active 4β-[2-(4-methoxybenzocyclobutenyl)ethyl] -5α-methoxymethyl-3-phenyl-thio-methylenefuran-2-ones 12 and 22, respectively, is studied and a stereoselective synthesis of (+)-$\text{trans}$-4,5-( 4-methoxybenzo) -1β,7aβ-(2α-methoxymethyl-5-oxofuro)hydrindane 1 is also described.     

New sesquiterpenes in a proposed russulaceae chemical defense system

In addition to already known sesquiterpene aldehydes, the lactaranes piperdial 1 and piperalol 2 were isolated from extracts of $\text{Lactarius piperatus}$, $\text{L. torminosus}$ and $\text{Russula queletii}$ (larger fungi).     

Enamine chemistry-XXVI: The [4 + 2] cycloaddition reactions of 3-amino-1-(4-nitrophenyl)-prop-2-ene-1-thione with electrophilic olefins and acetylenes

Enamino-thiones 1 prepared from the corresponding enaminones by thiation with Lawesson's Reagent, were allowed to react with 2-chloroacrylonitrile and dimethyl acetylenedicarboxylate giving dihydro-2$\text{H}$-thiopyrans, 2, and 4$\text{H}$-thipyrans, 3, respectively. The reaction of 1a with ethyl propiolate at room temperature afforded 4$\text{H}$-thipyrans, 4a, which on standing rearranged to 2$\text{H}$-thiopyran, 5a(1, 3 amide shift). The reaction of 1b with ethyl propiolate produced 4b and 5b. Some of the ¹³C NMR data are reported.     

Reductions stereoselectives d'acetyl β-lactames

Trans acetyl β-lactam $\text{3}$ is stereoselectively reduced by different reagents to afford the corresponding trans erythro and/or trans threo alcohols $\text{4}$ and $\text{5}$.     

Cyclic acetals as carbonyl blocking groups in the photo-fries rearrangement of acyl substituted aryl esters.

The ethylene acetals of $\text{o}$ and $\text{p}$-acetoxyacetophenone 3a,b, prepared from the corresponding hydroxyacetophenones by treatment with acetic anhydride in pyridine and subsequently with ethylene glycol and $\text{p}$-toluenesulphonic acid, give upon irradiation the expected photo-Fries products 4a,b (from 3a) or 6 (from 3b). These compounds are converted in part into diacetylphenols 5a,b as a consequence of a deacetalization, occurring to some extent during the irradiation and further in the chromatographic workup. The yields of the photoproducts and the $\text{ortho}$/$\text{para}$ ratio (in the case of 3a) are very similar to those given in the literature for phenyl acetate. By contrast, the acetoxyacetophenones 2a,b do not undergo any appreciable change upon irradiation,showing the deactivating effect of the acetyl side chain. Therefore, it is concluded that cyclic acetals are suitable carbonyl blocking groups in order to circumvent the deactivating effect of acyl substituents on the photo-Fries rearrangement of aryl esters.     

Enamine chemistry—XXIII: The [4+2] cycloaddition reactions between enaminothiones and electrophilic olefins and acetylenes

The enamino-thione, 1c, reacts with acrylonitrile and 2-chloroacrylonitrile at room temperature to give 3,4-dihydro-4-(1-pyrrolidinyl)-2$\text{H}$-thiopyrans, 4 and 5, respectively. The reaction between 1-aryl-3-(1-pyrrolidinyl) (piperidino)-apropene-1-thiones, 1a-c (1d-f), and dimethyl acetylenedicarboxylate gives 4-(1-pyrrolidiny)(piperidino)-4$\text{H}$-thiopyrans, 6a-c (6d-f). Compounds 1a-c (1d-f) and ethyl propiolate produce 2-(1-pyrrolidinyl) (piperidino)-2$\text{H}$-thiopyrans, 8a-c (8d-f), and a new type of rearrangement is observed. The 2$\text{D}$-thiopyran, 9, is formed from 1b and ethyl 3$\text{D}$-propiolate, which elucidates the mechanism. ¹H and ¹³C NMR data of 6 and 7 are discussed.     

Stereocontrolled synthesis of (+)-thienamycin from 3(R)-hydroxybutyric acid

The vinyloxyborane(5), prepared from (+)-$\text{S}$-phenyl-3($\text{R}$)-butanethioate, 9-BBN triflate and diisopropylethylamine, reacted with $\text{N}$-(3-benzyloxypropylidene)benzylamine to give the β-benzylamino thiol ester(6) in a moderate yield, which was efficiently converted to the optically pure thienamycin intermediate(10).     

Synthesis of novel macrobicyclic polyfunctional cryptands

A pathway yielding both $\text{syn}$ and $\text{anti}$-functionalized macrocycles derived from bis-tartaro-18-crown-6 (1) as well as a selective route to $\text{syn}$ compounds have been developed and applied to the synthesis of new macrobicyclic polyether cryptands (2) and (3), which may also be obtained by direct bridging of the dianhydride (4).     

Substituent influence on the indolization with pcl3 of some o,m,p-substituted phenylhydrazones

The indolization of deoxybenzoin $\text{o}$,$\text{m}$,$\text{p}$ (Me, MeO, Cl), $\text{p}$-NO₂ and $\text{m}$-EtO-phenylhydrazones (1) by the above reaction has been examined. All the reactions are carried out at room temperature and high yields of the corresponding indoles (2) are obtained even when -NO₂ substituent is present. In this case longer reaction time is necessary. Alkoxyphenylhydrazones give the corresponding indoles (2) in high yields without showing collateral reactions which indeed are present in several Fischer routes on these derivatives. $\text{m}$-Substituted phenylhydrazones (1) give a mixture of 4- and 6-substituted indoles in which the 6-isomer is always prevalent, a feature not inherent in the Fischer reactions. The regioselectivity is enhanced by the substituent steric hindrance increasing. The reaction can be also carried out at 0°C with a further improvement of its regioselectivity.     

Photo-Induced diels-alder reaction. A novel route to trans fused benzobicyclo-[5.3.O]decanes and [5.4.O]undecanes

Photoisomerization of $\text{cis}$-benzocycloheptenone to $\text{trans}$ benzocycloheptenone and its [4 + 2] cycloaddition with selected dienes is reported for the synthesis of $\text{trans}$ fused benzobicyclo[5.3.0]decanes 10, 12 and benzobicyclo [5.4.0]undecanes 13, 15.     

Photocyclization of n-[ω-(cycloalken-1-yl)alkyl]-and n-[ω-(inden-3-yl)alkyl]phthalimides : Synthesis of spiro-nitrogen multicyclic systems

Photolysis of the N-[ω-(cycloalken-1-yl)alkyl]phthalimides 6b-$\text{e}$ in each case gave a pair of stereoisomers of spiro-nitrogen multicyclic systems (9b-$\text{e}$) in moderate yields, whose stereochemistry was determined by means of chemical and spectroscopic analyses. Similarly, in N-[ω-(inden-3-yl)alkyl]-phthalimides (8), spiro-nitrogen macrocycles up to 13-membered 13a-$\text{c}$ were obtained in good yields     

Studies on organophosphorus compounds—XXXVI: Simple new routes to phosphorins from 2-hydroxy-, 2-mercapto-, and 2-aminobenzoic acids and their derivatives

2-Hydroxybenzoic acid heated with 2,4 - bis(4 - methoxyphenyl) - 1,3,2,4 - dithiadiphosphetane - 2,4 -disulfide, 1, gave 2 - (p - methoxyphenyl) - 4$\text{H}$ - 1,3,2 - benzoxathiaphosphorin - 4 - one 2 - sulfide, 3, and its thio-analogue, 4, while its ethyl or phenyl esters gave 4 as the sole product. 2 - Mercaptobenzoic acid and its ethyl ester when heated with 1 produced 3$\text{H}$ - 1,2 - benzodithiole - 3 - one, 8, 3$\text{H}$ -1,2 - benzodithiole - 3 - thione, 9, and 2- (p - methoxyphenyl) - 4$\text{H}$ - 1,3,2 - benzodithia - phosphorin - 4 - one 2 - sulfide, 10. The reaction of 2 -aminobenzoic acid with 1 gave 1,2 - dihydro - 2 - (p - methoxyphenyl) - 4$\text{H}$ - 3,1,2 - benzoxaphosphorin - 4 - one 2 - sulfide, 12. Reactions of 1 with methyl 2 - aminobenzoate and 2 - aminobenzamides are described. Mechanistic considerations for the formation of the heterocyclic phosphorus compounds are presented.     

Asymmetric total synthesis of stoechospermol using intramolecular (2+2) photocycloaddition reaction

The first asymmetric total synthesis of stoechospermol, a representative spatane diterpene having $\text{cis}$, $\text{anti}$, $\text{cis}$-tricyclo[5.3.0.0^2,6]decane ring system, was achieved. Using the intramolecular asymmetric (2+2) photocycloaddition reaction of the diastereomeric ester 11, the readily available butenolide 9 was transformed into the optically active dilactone 12a and 12b. Subsequent construction of tricyclic carbon ring system and introduction of substituents in a right stereochemistry gave rise to optically pure stoechospermol 1.     

Biosynthetic pathway of iridoid glucosides in Gardenia jasminoides f. grandiflora cell suspension cultures after iridodial cation formation

Administration of ²H- or ¹³C-labeled monoterpenes to $\text{Gardenia}$$\text{jasminoides}$ f. $\text{grandiflora}$ cell suspension cultures demonstrated that iridoid glucosides of the suspension cultures are biosynthesized, after iridodial cation formation from 10-oxocitral (3), via 8-epiiridodial (13), 8-epiiridotrial (14), boschnaloside (8-epiiridotrial glucoside) (12) and dehydroiridotrial glucoside (8). In addition, the coexistence of a route via iridodial cation (4), dehydroiridodial (6), dehydroiridotrial (15) and dehydroiridotrial glucoside (8) is conceivable.