SCAL

In SO form:

• stable in 100% TFA
• stable in reagent K
• stable in 50% piperidine
• stable in HF
• stable in Pd(0) treatment

In S form:

• stable in 50% piperidine
• cleaved by mixture K
• cleaved by 50% TFA

Reducing agents:

• 1M Me3SiCl/PPh3/DCM
• 1M PhSeSiMe3/DCM
• 0.1% HBr/AcOH

Applications: (i) Synthesis of peptides by combined Fmoc, Alloc and/or Boc strategy; (ii) Solid phase synthesis of cyclic peptides (synthesis by Fmoc strategy, deprotection of side chains, cyclization, reduction of SCAL, cleavage from the resin)

Patek, M., Lebl, M.: Tetrahedron Lett. 32, 3891, 1991