Synthesis ofd-Abrines by Palladium-catalyzed Reaction of ortho-Iodoanilines withN-Boc-N-methylalanyl-substituted Acetaldehyde and Acetylene

Abstract

A novel strategy to N-Boc-N-methyl-tryptophans (abrine derivatives) was developed that relies on the palladium-catalyzed annulation of ortho-iodoanilines 12 with either N-Boc-N-methyl-propargylglycine 16 or aldehyde 11. Both 11 and 16 can be prepared from D-serine. An alternative route to propargylglycine 16 utilizes an enantioselective propargylation reaction of glycine imine 17.

Synthesis of C3-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

“…The required zinc insertion compound 7 was prepared from L-serine ( 3 ). Thus, commercially available L-serine ( 3 ) was treated with acetyl chloride in methanol to give methyl ester 4 , which was subjected to N -Boc protection with di- tert -butyl dicarbonate (Boc 2 O) and triethylamine in tetrahydrofuran (THF) to obtain the N -Boc-serine methyl ester ( 5 ) in 93% yield [42]. Afterwards, the protected methyl ester 5 was subjected to iodination in the presence of iodine (I 2 ), triphenylphosphane (PPh 3 ) and imidazole in CH 2 Cl 2 at 0 °C to deliver the iodo derivative 6 in 63% yield [43–44].…”

Toward intrinsically colored peptides: Synthesis and investigation of the spectral properties of methylated azatryptophans in tryptophan‐cage mutants

“…This was based on the use of propargylglycine, with appropriate protecting groups present (Scheme ) . Thus, compound 21 was synthesized from enantiomerically pure iodoalanine 19 , followed by the zinc‐based cross‐coupling method with 1‐bromo‐2‐triethylsilylacetylene 20 as proposed by K nochel and coworkers . The palladium‐mediated heteroannulation was then performed, with respect to the previous investigations, in the presence of 1,1′‐bis‐(diphenylphosphino)ferrocene, which afforded the desired regioisomer 22 in 52% yield.…”

Synthesis of Indoles via Intermolecular and Intramolecular Cyclization by Using Palladium-Based Catalysts

“…The vital feature for regioselectivity was the steric hindrance of the t-butoxysilyl ether present on the alkynes pointing away from it (Scheme 79 (Equation (1))). The migratory insertion, however, occurred and minimized the steric crowding at the shortest carbon-carbon bond (Scheme 79 (Equation (2))), Furthermore, the Pd-catalyzed cross-coupling of derivatives of triethyl silyl propargyl glycine (262) with o-iodoanilines (261) by using Larock's conditions afforded N-ethyl-D-tryptophans (263) (Scheme 80) [226]. In 2010, Kondoh and co-workers carried out Pd-catalyzed cyclization of 1-alkynylphosphine sulfides (265) with o-iodoanilines (264) and subsequent desulfidation to afford 3-substituted 2-indolylphosphines (266).…”