Eric J. Leopold

Cleavage and deprotection of peptides from MBHA-resin with bromotrimethylsilane

Abstract A procedure was developed for the cleavage of thymosin α 1 from MBHA-resin with bromotrimethylsilane that would be pratctical for large scale manufacture of commercial quantities of the peptide.

Mechanism of presqualene pyrophosphate-squalene biosynthesis II. Synthesis of bifarnesol

Abstract A convenient synthesis of the racemate of bifarnesol (4), a proposed biochemical precursor of presqualene pyrophosphate and squalene, is described.

Presqualene alcohol, squalene, and sterol biosynthesis from bifarnesol

Abstract To cast light on the overall biosynthetic conversion of farnesol pyrophosphate to presqualene alcohol pyrophosphate (PSA), the biochemical precursor of squalene as well as all sterols, radiolabeled bifarnesol (1) was prepared and fed to Gibberella fujikuroi . The diol ( 1 ), acting as a surrogate for a previously suggested phosphorylated version of 1 , was converted to radiolabeled presqualene alcohol and squalene, as well as various sterols, including lanosterol and24-β-methylcholesta-5,7,9(11),22-tetraen-3β-ol, previously isolated from the same fungus. The results are interpreted to imply that a phosphorylated version of 1 may act as a bone fide intermediate in the biosynthesis of PSA, thereby rendering unlikely any type of concerted farnesyl/presqualene pyrophosphate change.

Presqualene alcohol from Gibberella fujikuroi

Abstract The sequencing of steps between farnesyl pyrophosphate (FPP) and squalene, in Gibberelia fujikuroi was investigated.