A novel method for Fmoc/tBu solution-phase peptide synthesis and the development of a new benzyl-type GAP protecting group is reported. This new GAP protecting group is utilized in place of a polymer support, facilitating C→N Fmoc peptide synthesis without chromatography, recrystallization, or polymer supports. The GAP group can be added and removed in high yield, and was used to synthesize over 1 gram of the immunostimulant, thymopentin, in high overall yield (83%) and purity (99%).
New silver‐catalyzed tunable dimerization and trimerization reactions of β‐alkynyl ketones have been established, enabling multiple C−C bond‐forming events to selectively access skeletally diverse spiroisochromenes with generally good yields. The silver‐enabled bicycloaddition of β‐alkynyl ketones with water offered hydroxylated spiroisochromenes. Without water, spiroisochromenes with a methylene moiety were obtained through catalytic 6‐endo‐dig oxo‐cyclization/[4+2] cycloaddition cascades by using pyridine as additive whereas employment of 1,1′‐binaphthyl‐2,2′‐diyl hydrogen phosphate (BiNPO4H) as a Brønsted acid catalyst rendered the unprecedented dispiro trimerization products through double C(sp3)–H functionalization.magnified image
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