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Application of two direct C(sp3)-H functionalizations for total synthesis of (+)-lactacystin.

Organic letters (2014-12-20)
Shun Yoshioka, Masanori Nagatomo, Masayuki Inoue
ABSTRACT

Herein, we report a new synthetic route from (S)-pyroglutaminol to (+)-lactacystin, a potent inhibitor of the 20S proteasome. The photoinduced intermolecular C(sp(3))-H alkynylation and intramolecular C(sp(3))-H acylation chemo- and stereoselectively constructed the tetra- and trisubstituted carbon centers, respectively. The obtained bicycle was transformed into the target compound in a concise manner. The present total synthesis demonstrates the power of the direct C(sp(3))-H functionalizations for the assembly of multiple functionalized structures of natural products.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
N-Acetyl-L-cysteine, Sigma Grade, ≥99% (TLC), powder
Sigma-Aldrich
N-Acetyl-L-cysteine, suitable for cell culture, BioReagent
Sigma-Aldrich
N-Acetyl-L-cysteine, BioXtra, ≥99% (TLC)
Supelco
N-Acetyl-L-cysteine, Pharmaceutical Secondary Standard; Certified Reference Material
USP
Acetylcysteine, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
Lactacystin, ≥90% (HPLC)
Acetylcysteine, European Pharmacopoeia (EP) Reference Standard