N-Carbamate-Assisted Stereoselective Synthesis of Chiral Vicinal Amino Sulfides

Abstract

[reaction: see text] Simply mixing amino alcohol A and thiol in toluene and TFA provided the corresponding amino sulfide B in excellent chemical yield and diastereoselectivity. A double SN2 process initiated by O-5 participation of the neighboring N-carbamate group was advanced to explain the overall retention of configuration at the chiral benzylic center.

Oxidative Nucleophilic Substitution (SNOx) of the Benzylic Position as a Tunable Synthesis of Tetrahydroisoquinoline Natural Alkaloid Analogues

“…In addition, in order to assess the viability of our synthetic strategy, the reaction of 24 with methyl thioglycolate was realized under the conditions established by Zhu and co-workers [32] (CF 3 CO 2 H/toluene, 0.03 ), which gave rise to 31a and 31b in 92 % yield with a 9:1 diastereoselectivity (Scheme 6).…”

“…This method allowed the formation of differently protected α-amino alcohols substituted at the benzylic position and suitable for the synthesis of the piperazine systems found in the ecteinascidin family. In addition, in order to assess the viability of our synthetic strategy, the reaction of 24 with methyl thioglycolate was realized under the conditions established by Zhu and co-workers [32] (CF 3 CO 2 H/toluene, 0.03 ), which gave rise to 31a and 31b in 92 % yield with a 9:1 diastereoselectivity (Scheme 6). Scheme 6.…”

Synthesis of β‐Hydroxy α‐Sulfanyl Esters by Using Nanocrystalline Magnesium Oxide

“…The sulfanyl group is a useful group for further transformations in organic synthesis. Low R fvalue isomer is anti-configured as revealed by X-ray diffraction study and consistent with the assignment of 1 H-NMR spectrum.Introduction.-b-Hydroxy a-sulfanyl esters have found widespread use in organic synthesis, particularily for the synthesis of natural products and pharmaceuticals [1]. The sulfanyl functionality is expected to act as a useful group for further transformations in the synthesis of a large number of target molecules [2].…”

Asymmetric Total Syntheses of Ecteinascidin 597 and Ecteinascidin 583

“…Unmasking of the Trocprotected primary alcohol under reductive conditions followed by chemoselective allylation of the phenol group provided compound 22, which was coupled with (R)-N-Troc-S-4,4',4''-trimethoxytritylcysteine to afford the corresponding ester 23 in excellent yield. [30] In this simple experiment, a complex reaction sequence involving O-MOM deprotection, 1,4elimination to give the orthoquinone methide, [31] and macrocyclization through an intramolecular Michael addition occurred in a highly ordered manner to bring about the key CÀS bond formation. Unfortunately, no combination provided the desired 10-membered lactone 25.…”

“…[29] Gratifyingly, the treatment of thiol 24 with TMSBr afforded the bridged macrocycle 25, after the phenol had been masked as the corresponding acetate, in 60 % yield. [30] In this simple experiment, a complex reaction sequence involving O-MOM deprotection, 1,4elimination to give the orthoquinone methide, [31] and macrocyclization through an intramolecular Michael addition occurred in a highly ordered manner to bring about the key CÀS bond formation.…”