摘要:

Recent advances and examples of the intramolecular Diels–Alder reaction are summarized and applications to the total synthesis of natural products, both completed and in progress, noted. A detailed discussion of trienes leading to bicyclo[4.3.0]nonene skeletons is followed by examples of bicyclo[4.4.0]decenes and adducts arising fromortho-quinodimethane precursors. Cycloadditions affording bicyclo[n.4.0] systems and bridged-ring adducts from cyclic dienes conclude this survey which is followed by a discussion of unreactive trienes and a brief analysis of synthetic strategy to complete the review.

ISSN:0008-4042    

DOI:10.1139/v84-037

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The reactivity of carbonyl and aromatic compounds for the nucleophilic displacement is investigated theoretically. LUMO (lowest unoccupied MO) obtained by the mixing of the π* MO with the σ* MO is a uniform criterion of the relative reactivity of substrates. The presence or absence of the tetrahedral intermediate is found to depend on the energy difference between the π* and σ* MO's.

ISSN:0008-4042    

DOI:10.1139/v84-038

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The synthesis of a series of purine analogues of the acyclonucleoside compound A* (A-Star,1) is described. Compounds in this series have been shown to have pronounced activity against herpesviruses. These compounds have been designated "the glycerosides". The glyceropurines are described in this report. Nucleotides have been constructed containing glyceroadenine (A*, compound1). These nucleotides are resistant to degradation by phosphodiesterases. The compound A* is both a poor substrate and a poor inhibitor of adenosine deaminase.

ISSN:0008-4042    

DOI:10.1139/v84-039

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Using 4-31G basis sets, the geometries of H2CS, HFCS, and F2CS as well as their protonated cations were optimized. In each case, three protonation sites, S, C, and H (for H2CS) or F (for HFCS and F2CS) were considered. The H or F protonation leads to molecular complexes of the form HX … YCS+. For H2CS and F2CS, the S-protonation site is favored, whereas for HFCS the linear complex HF … HCS+is the most stable protonated form. Predicted proton affinities are 177.4 for H2CS (180.9 experimental), 172.0 for HFCS, and 149.1 kcal/mol for F2CS.

ISSN:0008-4042    

DOI:10.1139/v84-040

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Grandiflorine, a minor alkaloid ofArgemonegrandifloraSweet subsp•grandiflora, is shown to be identical with ribasine (and most likely limogine) and have the carbinolamine ether-bridged indanobenzazepine structure1.

ISSN:0008-4042    

DOI:10.1139/v84-041

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Diamagnetic and paramagnetic amine derivatives of cellulose have been prepared from selectively oxidized cellulose precursors via the reductive amination method using sodium cyanoborohydride. 4-Amino-2,2,6,6-tetramethylpiperidine-1-oxyl was employed in the syntheses of nitroxide spin labelled cellulose derivatives4and5from 3-oxy-cellulose (1) and 6-O-triphenylmethyl-2-oxy-cellulose (2). Conversion of the linear polymer1into a highly branched, water soluble 3-deoxy-cellulose derivative6was accomplished by attachment of glucosamine side chains. 3-Amino-3-deoxy-cellulose7was obtained using ammonium acetate. A novel type of organometallic cellulose conjugate8was prepared by condensation of2andp-toluidine chromium tricarbonyl. Similarly, 1,10-diazo-18-crown-6 was added to2to form the crown ether derivative9. The synthetic strategies involving either 6-Oprotected or unprotected oxy-cellulose intermediates are compared in terms of reaction yields and product properties.

ISSN:0008-4042    

DOI:10.1139/v84-042

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Several sources of the fluoride anion have been compared as electron donors in the hydrogen bond assisted alkylation of phenols.

ISSN:0008-4042    

DOI:10.1139/v84-043

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Fourier transform infrared spectra of several N7-bound cations of guanosine-5′monophosphate disodium salt (5′-GMPNa2), such as N7-H+GMP, N7-MeGMP, and N7-MGMP, where Me = CH3+and M = divalent metal ions, Cd, Mn, Co, Ni, Cu, Pt, and Mg, have been recorded and a correlation between the spectral changes and the nature of the electrophile (H+, CH3+, and M2+) bound has been established. Spectroscopic evidence shows that methylation of the N7-position of 5′-GMPNa2causes larger perturbation on the guanine ring system than protonation or metalation, in the order Me+ > H+ > M2+. The effect of an N7-electrophilic attack on the vibrational frequencies of the purine, the sugar, and the phosphate group is discussed.

ISSN:0008-4042    

DOI:10.1139/v84-044

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The presence of the 4α-methyl group in olefin4or in conjugated ketone10prevents catalytic hydrogenation from the α side, leading exclusively tocis-fused decalins.

ISSN:0008-4042    

DOI:10.1139/v84-045

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The O—O stretching frequencies of some alkyl substituted 1,2-dioxacyclohexanes are near 730 cm−1and those of some alkyl substituted 1,2-dioxetanes are in the range 670 ± 20 cm−1. Alkoxy substituents cause the frequency to increase; that for tetramethoxy-1,2-dioxetane is 752 cm−1. Alkoxy substituents appear to stabilize peroxides.

ISSN:0008-4042    

DOI:10.1139/v84-046

出版商:NRC Research Press    

年代:1984

数据来源: NRC