Concise Synthesis of (-)-Veratramine and (-)-20--Veratramine via Aromative Diels-Alder Reaction.

A concise and convergent synthesis of the isosteroidal alkaloids veratramine and 20--veratramine has been accomplished. A Horner-Wadsworth-Emmons olefination joins two chiral building blocks of approximately equal complexity and a transition-metal catalyzed intramolecular Diels-Alder cycloaddition-aromatization cascade constructs the tetrasubstituted arene. Other key steps include a highly diastereoselective crotylation of an -sulfonyl iminium ion and an Eschenmoser fragmentation.

Improving Molecular Iron Ammonia Oxidation Electrocatalysts via Substituent Effects That Modulate Standard Potential and Stability.

Molecular ammonia oxidation (AO) catalysis is a rapidly evolving research area. Among the catalysts studied, featuring metals including ruthenium, iron, manganese, nickel, and copper, polypyridyl iron complexes are attractive owing to fast catalytic rates and significant turnover numbers (TON). Building upon our previous work on AO using [(TPA)Fe(MeCN)] and [(BPM)Fe(MeCN)], this study investigates factors that impact rate and TON within and across catalyst series based on polypyridyl ligand frameworks.

Mechanism of a Luminescent Dicopper System That Facilitates Electrophotochemical Coupling of Benzyl Chlorides via a Strongly Reducing Excited State.

Photochemical radical generation has become a modern staple in chemical synthesis and methodology. Herein, we detail the photochemistry of a highly reducing, highly luminescent dicopper system [Cu] (* ≈ -2.7 V vs SCE; ≈ 10 s) within the context of a model reaction: single-electron reduction of benzyl chlorides.

Enhanced Ammonia Oxidation Catalysis by a Low-Spin Iron Complex Featuring Coordination Sites.

The goal of using ammonia as a solar fuel motivates the development of selective ammonia oxidation (AO) catalysts for fuel cell applications. Herein, we describe Fe-mediated AO electrocatalysis with [(bpyPyMe)Fe(MeCN)], exhibiting the highest turnover number (TON) reported to date for a molecular system. To improve on our recent report of a related iron AO electrocatalyst, [(TPA)Fe(MeCN)] (TON of 16), the present [(bpyPyMe)Fe(MeCN)] system (TON of 149) features a stronger-field, more rigid auxiliary ligand that maintains -labile sites and a dominant low-spin population at the Fe(II) state.

Tricyclic CNS active agents by intramolecular Oxa-Pictet-Spengler reaction.

Mitsunobu inversion of the (S)-configurated lactate (S)-7, which is prepared in four steps starting from (S)-tyrosine, leads to the (R)-configurated lactate (R)-7. The key step in the transformation of the enantiomeric lactates (S)-7 and (R)-7 into the benzomorphan analogous tricycles (R,S)-16a,b, (S,R)-16a,b, (S,S)-22, and (R,R)-22 is an intramolecular Oxa-Pictet-Spengler reaction: The amides (S)-13, (R)-13, (S)-19 and (R)-19, in which the carbonyl moiety-masked as an acetal-is linked to the 2-phenylethanol moiety, are cyclized to give the tricyclic amides (R,S)-15, (S,R)-15, (S,S)-21, and (R,R)-21, respectively. In a concentration of 100 microM both enantiomers of 16a, 16b, and 22 are not able to compete with 3H-(+)-MK 801 for the phencyclidine binding sites of NMDA receptors.

[Synthesis of homochiral 5,9-epoxybenzocyclooctenes with amino substitutents: relationship between structure and CNS activity].

This paper deals with the synthesis and psychopharmacological effects of variations of the sedative and analgesic tricyclic amines 3a and 3b: Starting with the homochiral ketone 4 the amines 5 (primary amino group in equatorial position), 7 (axially oriented dimethylamino group), 9 (additional phenyl residue in position 7), 13b, and 14b (equatorially and axially arranged dimethylaminomethyl group) and 23 and 24 (axial amino group shifted to position 9) are prepared. BBr3 cleaves the phenolic ethers of the secondary amine (+/-)-3a to yield the aminodiphenol (+/-)-10. -Keeping mice under observation for behavioral anomalies (Irwin screen) and analgesic activity (writhing test) shows, that the amines 5, 7, 9, (+/-)-10, 13b, 14b, and 23 do not reach the sedative and analgesic effects of the amines 3a and 3b, described by us.

[Synthesis of enantiomerically pure 6,10-epoxybenzocycloocten-7-amines with CNS activity].

In an oxa-Pictet-Spengler reaction the methyl (S)-phenyllactate 6 and methyl levulinate (7a) are condensed to the 2-benzopyrans cis-8a and trans-8a, which react with CH3I to yield the dimethyl ethers cis-9a and trans-9a. Cis-9a and trans-9a can be separated by medium pressure liquid chromatography. In the subsequent Dieckmann-Cyclisation cis-9a is transformed to the laevorotatory beta-ketoester (-)-10a, while the dextrorotatory enantiomer (+)-10a is obtained from trans-9a after C-3-epimerisation.