摘要:

The malonate anion intramolecular displacement of propargylic or allylic chlorides, and primary bromide, in thirteen- and fourteen-carbon chains containing either two, one, or no unsaturation sites, yields the corresponding 13- and 14-membered ring compounds under conditions of medium dilution.

ISSN:0008-4042    

DOI:10.1139/v87-011

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Dimethyl 6,6-dimethyl-5,7-dioxobicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate (8) on irradiation in acetophenone gives dimethyl 6,6-dimethyl-4,7-dioxotricyclo[3.2.1.02,8]octane-1,8-dicarboxylate (13), which on treatment with lithium dimethylcuprate followed by monodecarbomethoxylation gives methyl 4,4-endo-8-trimethyl-3,6-dioxo-cis-bicyclo[3.3.0]octane-1-carboxylate (17). Similar irradiation of dimethyl 4,6,6-trimethyl-5,7-dioxobicyclo[2.2.2]oct-2-ene-2,3-dicarboxylate (24) and its 7,7-ethylenedioxy derivative (25) followed by treatment with DBU and concentrated H2SO4, respectively, gives dimethyl 3-hydroxy-4,4,8-trimethyl-6-oxo-cis-bicyclo[3.3.0]-octa-2,7-diene-1,2-dicarboxylate (30). This, on acetylation, reduction with NaBH4/CeCl3, methanolysis, monodecarbomethoxylation, and hydrogenation, gives methylendo-6-hydxoxy 4,4-endo-8-trimethyl-3-oxo-cis-bicyclo[3.3.0]octane-1-carboxylate (38), while on reduction with Li/NH3followed by monodecarbomethoxylation it gives a methyl 6-hydroxy-4,4-exo-8-trimethyl-3-oxo-cis-bicyclo[3.3.0]octane-1-carboxylate (33).

ISSN:0008-4042    

DOI:10.1139/v87-012

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Reaction of Me3SnLi with 1 equivalent of CuBr•Me2S, PhSCu, Me2(MeO)C—C≡C—Cu, or CuCN in tetrahydrofuran (THF) affords the (trimethylstannyl)copper(I) reagents Me3SnCu•Me2S (1) and [Me3SnCuY]Li (Y = PhS (2), Me2(MeO)C—C≡C (4), CN (5)), respectively. Similarly, treatment of a THF solution of Me3SnLi with 0.5 equivalent of CuBr•Me2S provides (Me3Sn)2CuLi (3), while reaction ofn-Bu3SnLi with PhSCu (1 equivalent) gives [n-Bu3SnCuSPh]Li (6). Reagents2and6readily transfer (in a conjugate sense) the R3Sn group to conjugated enones (e.g.7–9) and structurally simple enoates (e.g.10), but do not react with β,β-disubstituted α,β-unsaturated esters (e.g.11–13). Reaction of reagent2with the enone26under "normal" conditions produces, in addition to the expected ketone28, a significant amount of the double conjugate addition product30. A similar result is obtained with ethyl propenoate (27). However, reaction of26and27with reagent2in the presence of acetic acid provides cleanly and efficiently the "simple" conjugate addition products28and29, respectively. Reagent1does not react, or reacts very sluggishly, with α,β-unsaturated carbonyl compounds. β-Trialkylstannyl α,β-unsaturated ketones (e.g.37–46) can be produced smoothly and efficiently by reaction of the corresponding β-iodo enones (e.g.32–36) with reagents2(or1) and6.

ISSN:0008-4042    

DOI:10.1139/v87-013

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A few types of amines XNH2were investigated for the formation of β-lactams via the cycloaddition of the corresponding Schiff bases with azidoacetyl chloride. Among the β-lactams formed, only theN-p,p′-dimethoxybenzhydryl compounds could be transformed to N-unsubstituted azetidinones by removal of the N-substituent with ceric ammonium nitrate. Conversion of those N-unsubstituted intermediates to 3-acylated monobactams was studied in the 4-styryl series.

ISSN:0008-4042    

DOI:10.1139/v87-014

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Total synthesis ofdl-coccuvinine1aanddl-coccolinine2a, "abnormal-type" erythrinan alkaloids lacking the C(16) O-function at the aromatic ring, was effectively achieved by using the Diels–Alder reaction of dioxopyrroline. Isoquinolinopyrrolinedione6a, a key dienophile, was synthesized via the tetrahydroisoquinoline5a, which was prepared by Bischler–Napieralski cyclization of the amide4aat the unactivated position. The Diels–Alder adduct7aof 1,3-bis(trimethylsilyloxy)-butadiene with6awith converted stereoselectively into these alkaloids in short steps.

ISSN:0008-4042    

DOI:10.1139/v87-015

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

13C Nuclear magnetic resonance spectroscopy is an exceptionally useful tool for the structure determination of diterpenoid alkaloids. A detailed study of the1H and13C nmr spectra of aconitine and 3-deoxyaconitine has permitted definite assignments to all the carbon atoms of the molecule. Chemical shift revisions have been suggested for certain carbon atoms of the C19-diterpenoid alkaloids. Chemical examination ofAconitumcolumbianumNutt. ssp.columbianum,A.forrestiiStapf,DelphiniumtatsienenseFranch., andD.vestitumWall, resulted in the isolation of several new C19-diterpenoid alkaloids. The structure derivation of those alkaloids was based mainly on13C nmr spectroscopic evidence.

ISSN:0008-4042    

DOI:10.1139/v87-016

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The synthesis of strained tricyclic azetidinones was achieved by free radical cyclization of N-substituted azetidinones involving a tributyltin hydride/AIBN mediated chain reaction. The 5-exocyclization led to benzo carbapenems10,12, and13, which were relatively unstable in solution. The 6-exomode, however, afforded stable benzo carbacephems20,22,24, and25.

ISSN:0008-4042    

DOI:10.1139/v87-017

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The preparation of 2-carboxylated-1,3-dienes from carbomethoxy vinylphosphonates and 2-mercaptocarbonyl compounds has been shown to give stereoisomeric mixtures. This may be due to the formation of stereoisomers of the intermediate 2,5-dihydrothiophenes and (or) to the occurrence of both modes of disrotatory sulfur dioxide elimination.

ISSN:0008-4042    

DOI:10.1139/v87-018

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene are described. The sequence employs a "blocked" cyclopentadiene in which the cyclopropane unit also serves as a latent methyl group. Thus intramolecular [4 + 2] cycloaddition of the substituted methyl spiro[2.4]hepta-4,6-dien-1-yl-2-pentenoate13caffords 5-benzyloxy-6-isopropyl-8-carbomethoxytetracyclo[5.4.01,7.02,4.02,9]undec-10-ene (14c), which after selective hydrogenolysis generates the tricyclo[4.4.01,6.02,8]decane (sinularene) ring system. Removal of the secondary hydroxyl function by elimination and hydrogenation (Ph3P/CCl4/CH3CN; H2/Pd/C), reduction of the methyl ester (LiAlH4), and introduction of the exocyclic double bond (acetate pyrolysis, 550 °C) completes the synthesis of (±)-sinularene in 12 steps from aldehyde7. A parallel series of reactions employing the isopropyl triene epimer13aaffords (±)-5-epi-sinularene. X-ray analyses of the triene13aand the adduct14aare also reported.

ISSN:0008-4042    

DOI:10.1139/v87-019

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Convergent syntheses of the benz[a]anthraquinone natural products X-14881 C (2c) and ochromycinone (2d) have been achieved using aromatic directed metalation strategies. Key steps involve (a) the condensations of dilithiatedcis-tetralol (13a) with the aldehydoo-anisamide14and of methoxymethyl protected aldehyde17bwith lithiatedo-anisamide (18) to give, after acid-catalyzed cyclization, the phthalide16, and (b) the regiospeciflc hydroxyselenylation of anthraquinone22to provide the hydroxyselenide23.

ISSN:0008-4042    

DOI:10.1139/v87-020

出版商:NRC Research Press    

年代:1987

数据来源: NRC