On the mechanism of sulfonamide cleavage by arene anion radicals

Nms-Amides: An Amine Protecting Group with Unique Stability and Selectivity

p-Toluenesulfonyl (Tosyl) and nitrobenzenesulfonyl (Nosyl) are two of the most common sulfonyl protecting groups for amines in contemporary organic synthesis. While p-toluenesulfonamides are known for their high stability/robustness, their use in multistep synthesis is plagued by difficult removal. Nitrobenzenesulfonamides, on the other hand, are easily cleaved but display limited stability to various reaction conditions. In an effort to resolve this predicament, we herein present a new sulfonamide protecting group, which we term Nms. Initially developed through in silico studies, Nms-amides overcome these previous limitations and leave no room for compromise. We have investigated the incorporation, robustness and cleavability of this group and found it to be superior to traditional sulfonamide protecting groups in a broad range of case studies.

Improved Synthesis of the Amine Fragment of FR901464 and Thailanstatins through the Development of a Convenient N-Detosylation Method

FR901464 and thailanstatins are potent cytotoxic natural products that share an amine-containing tetrahydropyran ring. We previously reported the synthesis of the tetrahydropyran component. Here, we changed the protecting group for the amine from Boc to tosyl, improving yields and the time economy. A highlight of the revised synthetic scheme is the use of lithium, t-butanol, and ethylenediamine in THF (nontraditional Birch reduction conditions) for the N-detosylation.

The Detosylation of Chiral 1,2-Bis(tosylamides)

The deprotection of chiral 1,2-bis(tosylamides) to their corresponding 1,2-diamines is mostly unsuccessful under standard conditions. In a new methodology, the use of Mg/MeOH with sufficient steric additions allows the facile synthesis of 1,2-diamines in 78-98% yields. These results are rationalized using density functional theory and the examination of inner and outer-sphere reduction mechanisms.

A general method for palladium-catalyzed reactions of primary sulfonamides with aryl nonaflates

A general method for Pd-catalyzed sulfonamidation of aryl nonafluorobutanesulfonates (aryl nonaflates) is described. A biaryl phosphine ligand, t-BuXPhos, formed the most active catalyst, and K(3)PO(4) in tert-amyl alcohol was found to be the optimal base-solvent combination for the reaction. The reaction conditions were tolerant of various functional groups such as cyano, nitro, ester, aldehyde, ketone, chloride, carbamate, and phenol. Heterocyclic aryl nonaflates were found to be suitable coupling partners. High yields of the coupled products were obtained from the reactions between inherently disfavored substrates such as electron-rich nonaflates and electron-poor sulfonamides. Kinetic data suggest reductive elimination to be the rate-limiting step for the reaction. The only limitation of this methodology that we have identified is the inability of 2,6-disubstituted aryl nonaflates to efficiently participate in the reaction.

Asymmetric synthesis of anti-α-substituted β-amino ketones from sulfinimines

Previously unknown, enantiopure, β-amino ketones were prepared in modest yield by addition of lithium reagents to N-sulfinyl anti-α-substituted β-amino Weinreb amides. Grignard reagents failed to add to these Weinreb amides in contrast to the syn-α-substituted isomers which did. The anti-α-substituted β-amino Weinreb amides were prepared by addition of LiN(OMe)Me to the corresponding N-sulfinyl anti-α-substituted β-amino esters because α-alkylation of N-sulfinyl β-amino Weinreb amide enolates resulted in poor diastereoselectivities.

Asymmetric synthesis of cyclic cis-beta-amino acid derivatives using sulfinimines and prochiral Weinreb amide enolates

Cyclic cis-beta-amino Weinreb amides, valuable building blocks for the asymmetric synthesis of cyclic beta-amino acids derivatives, are readily prepared via ring-closing metathesis of sulfinimine-derived N-sulfinyl beta-amino diene Weinreb amides. These unsaturated cyclic cis-beta-amino Weinreb amides are valuable building blocks for the asymmetric synthesis of cyclic beta-amino acid derivatives.

Synthesis of Bisubstrate Inhibitors of Porphobilinogen Synthase fromPseudomonas aeruginosa

Porphobilinogen synthase (PBGS) synthesizes porphobilinogen 2 (PBG), the common precursor of all natural tetrapyrroles, through an asymmetric condensation of two molecules of 5-aminolevulinic acid 1 (ALA). Symmetrically linked dimers 7-11 derived from levulinic acid 3 (gamma-oxovaleric acid) have been synthesized to mimic the assumed bisubstrate bound to the active site of the enzyme. Their inhibition potential was characterized by determination of the IC(50) and K(i) values using PBGS from Pseudomonas aeruginosa. The polarity and the size of the functional group linking the two levulinic acid 3 units have a strong influence on the inhibition behavior.

Double Reduction of Cyclic Aromatic Sulfonamides: A Novel Method for the Synthesis of 2- and 3-Aryl-Substituted Cyclic Amines

The facile double reduction of bicyclic aromatic sulfonamides was used to synthesize a variety of 2- and 3-aryl-substituted pyrrolidines and 2-phenylpiperidine. The method features a combined nitrogen protection and a traceless tether for the transposition of the aromatic moiety from nitrogen to carbon.

Synthesis of (2R,3R,4S)-2-hydroxymethylpyrrolidine-3,4-diol from (2S)-3,4-dehydroproline derivatives

(2R,3R,4S)-2-Hydroxymethylpyrrolidine-3,4-diol (1,4-dideoxy-1,4-imino-D-ribitol) was synthesized in five steps from N-protected (2S)-3,4-dehydroproline methyl esters. The stereoselective reaction of osmium tetraoxide with dehydroproline derivatives gave high yields of (2S,3R,4S)-3,4-dihydroxyprolines (2,3-trans-3,4-cis-3,4-dihydroxy-L-prolines) accompanied by small amounts (< 15%) of the diastereomeric (2S,3S,4R)-3,4-dihydroxyprolines (2,3-cis-3,4-cis-3,4-dihydroxy-L-prolines). The mixture of the diastereomeric glycols was converted into the isopropylidene acetals, and the isomers separated efficiently on a preparative scale. The resulting protected (2S,3R,4S)-3,4-dihydroxyproline methyl ester was reduced (LiBH4) to the 2-hydroxymethylpyrrolidine and deprotected, resulting in the production of (2R,3R,4S)-2-hydroxymethylpyrrolidine-3,4-diol in high yield and in high purity. The 1H and 13C NMR signals of the product have been unambiguously assigned using two-dimensional NMR techniques, and the identity of the title pyrrolidine confirmed by comparisons of its spectra with those reported for the authentic material.