Enantioselective deprotonation of protected 4-hydroxycyclohexanones

1994 ◽  
Vol 72 (7) ◽  
pp. 1699-1704 ◽  
Author(s):  
Marek Majewski ◽  
John MacKinnon
Keyword(s):  
Hydroxy Group ◽  
Silyl Ether ◽  
Lithium Amides ◽  
Enol Acetates ◽  
Optically Pure ◽  
Derivatives Of ◽  
Enantioselective Deprotonation

A series of derivatives of 4-hydroxycyclohexanone (1a–g) with the hydroxy group protected as a silyl ether (1a, b), ether (1d, g), an acetal (1c), or an ester (1e, f) were deprotonated with chiral, optically pure, lithium amides 3–9. The resulting non-racemic enolates were trapped as enol acetates. The enantioselectivity of deprotonation was up to 74% ee.

Enantioselective ring opening of tropinone. A new entry into tropane alkaloids

1997 ◽  
Vol 75 (6) ◽  
pp. 754-761 ◽  
Author(s):  
Marek Majewski ◽  
Ryszard Lazny ◽  
Agnieszka Ulaczyk
Keyword(s):  
Ring Opening ◽  
Stereoselective Synthesis ◽  
Tropane Alkaloids ◽  
Amine Hydrochloride ◽  
Lithium Amides ◽  
Ring Opening Reaction ◽  
Alkyl Chloroformates ◽  
Optically Pure ◽  
Enantioselective Deprotonation

The lithium enolate of tropinone reacts with alkyl chloroformates to give 6-N-carboalkoxy-N-methyl-2-cycloheptenones (4). These compounds can be produced enantioselectively, in up to 95% ee, if chiral lithium amides (derived from optically pure amines 5–7) are used for deprotonation of tropinone in the presence of additives. The effect of additives such as LiCl, LiBr, LiF, LiClO4, CeCl3, ZnCl2, LiOH, TMEDA, HMPA, and DMPU on enantioselectivity of this deprotonation–ring opening sequence varies from slight to very large depending on the chiral amide – additive combination. Especially large increases in enantioselectivity are observed when the chiral, C2 symmetrical, lithium bis-α,α′-methylbenzylamide (Li-5a) is used with one equivalent of LiCl. This reagent is best generated in situ from the corresponding amine hydrochloride and n-BuLi (2 equiv.). The ring-opening reaction combined with transposition of the carbonyl group (via Wharton reaction or allylic oxidation) provides a new method of stereoselective synthesis of tropane alkaloids having a protected hydroxyl at C-6 or C-7 (6β- and 7β-acetoxytropanes 14a, b) and physoperuvine (19). Keywords: enantioselective deprotonation, tropane alkaloids.

Studies on enolate chemistry of 8-thiabicyclo[3.2.1]- octan-3-one: enantioselective deprotonation and synthesis of sulfur analogs of tropane alkaloids

2001 ◽  
Vol 79 (11) ◽  
pp. 1792-1798 ◽  
Author(s):  
Marek Majewski ◽  
Marc DeCaire ◽  
Pawel Nowak ◽  
Fan Wang
Keyword(s):  
Acetic Anhydride ◽  
Key Words ◽  
Carboxylic Acids ◽  
Alkylating Agents ◽  
Tropane Alkaloids ◽  
Lithium Amides ◽  
Lithium Enolate ◽  
Unsaturated Carboxylic Acids ◽  
Derivatives Of ◽  
Enantioselective Deprotonation

Enantioselective deprotonation of 8-thiabicyclo[3.2.1]octan-3-one (1) with chiral lithium amides, followed by reactions with electrophiles affords sulfur analogs of tropane alkaloids of pyranotropane family. Thus, deprotonation of 1 with (S)-N-(diphenyl)methyl-1-phenylethylamine (11d), followed by the reaction of the resulting nonracemic enolate with benzaldehyde gives the corresponding aldol product as one diastereoisomer (exo, threo) and in high enanatiomeric purity (95% ee). Trimethylsilyl chloride, acetic anhydride, and acyl cyanides react readily with the lithium enolate to give the corresponding derivatives of 1, however common alkylating agents fail to provide C-alkylated products. The reaction with acyl cyanides derived from α,β-unsaturated carboxylic acids (e.g., cinnamoyl cyanide) can be utilized in synthesis of thia-analogs of tropane alkaloids physoperuvine and isobellendine (13, 15).Key words: enantioselective deprotonation, tropane alkaloids.

Coupling of Steroid O-(Carboxymethyl)oxime Derivatives with Amino Alcohols

1996 ◽  
Vol 61 (2) ◽  
pp. 288-297 ◽  
Author(s):  
Vladimír Pouzar ◽  
Ivan Černý
Keyword(s):  
Amino Acids ◽  
Hydroxy Group ◽  
Building Blocks ◽  
Amino Alcohols ◽  
New Approach ◽  
Alternative Synthesis ◽  
Oxime Derivatives ◽  
A Chain ◽  
Derivatives Of

New approach to the preparation of steroids with connecting bridge, based on an O-carboxymethyloxime (CMO) structure, and with terminal hydroxy group, is presented. 17-CMO derivatives of 3β-acetoxy- and 3β-methoxymethoxyandrost-5-en-17-one were condensed with α,ω-amino alcohols to give derivatives with a chain of seven to nine atoms. After THP-protection, these compounds were converted to 3-keto-4-ene derivatives. An alternative synthesis consisted in transformation of 17-CMO derivatives with bonded amino acids by reduction of the terminal carboxyl. The resulting compounds were designed as building blocks for the preparation of bis-haptens for sandwich immunoassays.

Synthesis of Sterically Congested Carbamates of Carbohydrates through Organic Base Catalysis

Synthesis ◽  
2019 ◽  
Vol 51 (15) ◽  
pp. 2897-2908 ◽  
Author(s):  
Anji Chen ◽  
Dan Wang ◽  
Lalith P. Samankumara ◽  
Guijun Wang
Keyword(s):  
Hydroxy Group ◽  
Current Method ◽  
Building Blocks ◽  
Base Catalysis ◽  
Organic Base ◽  
Molecular Assemblies ◽  
Effective Catalyst ◽  
Organic Bases ◽  
Derivatives Of ◽  
General Method

4,6-O-Benzylidene acetal protected α-methoxy d-glucose and d-glucosamine are useful building blocks for the syntheses of carbohydrate derivatives and functional molecular assemblies. In this research, we have developed a general method for the preparation of C-3 carbamate derivatives of densely functionalized glucose and glucosamine with isocyanates using organic bases as catalysts. Without a suitable catalyst, the C-3 hydroxy group of the glucosamine derivative could not be converted into the corresponding carbamates when treated with isocyanates. Several organic bases were screened as the catalysts for the reactions, and we discovered that 5.0 mol% of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was an effective catalyst for the carbamoylation reaction. A library of both alkyl and aryl carbamate derivatives of the two sterically congested carbohydrates have been effectively synthesized using the current method.

Modellreaktionen zur Plumbagin-Synthese, 2. Mitteilung 5-Amino-1-naphthol als Startkomponente / Model Reactions for Plumbagin Synthesis, 2nd Communication 5-Amino-1-naphthol as Starting Compound

1987 ◽  
Vol 42 (12) ◽  
pp. 1578-1584 ◽  
Author(s):  
Hans Möhrle ◽  
Hubertus Folttmann
Keyword(s):  
Hydroxy Group ◽  
Mannich Bases ◽  
Starting Compound ◽  
Derivatives Of ◽  
Nitrosylsulfuric Acid ◽  
Model Reactions

AbstractThe aminomethylation of 5-amino-1-naphthol (1) and 5-acetamido-1-naphthol (9) is examined. While the hydrogenolysis of the phenol Mannich bases derived from 1 cannot be accomplished, the derivatives of 9 react easily. The oxidation of the 2-methylphenol compounds 5 and 18 to the corresponding quinones may performed with Fremy's salt. The following transforming of the amino to the hydroxy group by nitrosylsulfuric acid succeeds with small yield only.

Esters of arylpropionic acids with 1,2:5,6-di-O-isopropylidene- and 1,2-O-isopropylidene-α-D-glucofuranose

1987 ◽  
Vol 52 (3) ◽  
pp. 766-774 ◽  
Author(s):  
Jiří Svoboda ◽  
Karel Čapek ◽  
Jaroslav Paleček
Keyword(s):  
Fractional Crystallization ◽  
Kinetic Resolution ◽  
Methyl Esters ◽  
Optically Pure ◽  
Derivatives Of

On fractional crystallization of 3-O-(2-(2-fluoro-4-biphenylyl)propionyl)-, 3-O-(2-(4-isobutylphenyl)propionyl)- and 3-O-(2-(6-methoxy-2-naphthyl)propionyl)-1,2 :5,6-di-O-isopropylidene-α-D-glucofuranoses V-VII optically pure R-diastereoisomers were isolated. The derivatives of 1,2-O-isopropylidene-α-D-glucofuranose obtained on partial deacetylation of esters V-VII were separated chromatographically to R and S-diastereoisomers. Their hydrolysis or transesterification afforded optically pure arylpropionic acids or their methyl esters, respectively. Kinetic resolution of the acids gives rise to esters V-VII enriched in R-diastereoisomer.

ChemInform Abstract: Stereochemistry of Enantioselective Deprotonation of 4-Substituted Cyclohexanones by Chiral Bidentate Lithium Amides.

ChemInform ◽  
2010 ◽  
Vol 28 (17) ◽  
pp. no-no
Author(s):  
M. TORIYAMA ◽  
K. SUGASAWA ◽  
M. SHINDO ◽  
N. TOKUTAKE ◽  
K. KOGA
Keyword(s):  
Lithium Amides ◽  
Enantioselective Deprotonation
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