A Sophisticated Resin for the Solution of Synthesis Challenges. TentaGel® XV resin (XV stands for "Extended Swelling Volume") is a new member of the TentaGel® family. Modifications on the polystyrene backbone change the swelling properties of the PEG grafted resin. Swelling properties are in the same range or even higher compared to PEGA or Chematrix resins. The polar PEG spacers allow the composite resin to swell in a wide range of solvents including water, methanol, DMF, DCM. Nevertheless, the handling is still very easy and similar to other TentaGel® resins. The high swelling creates an extended reaction space. This enlarged reaction volume meets the requirement for ideal conditions for the synthesis of difficult sequences, aggregating peptides, mini proteins and PNAs in high purities and excellent yields. Purified yield of PNA4-peptide15-PNA11 Resin yield [%] Wang resin 0 Chematrix 20 TentaGel® XV 32 This resin is derived from TentaGel® NH2 resin by coupling with the 4-carboxytrityl linker. For further reactions the alcohol group has to be converted to the chloride and then used immediately. This highly acid sensitive linker is useful for the immobilization of alcohols, amines and carboxylic acids. Cleavage is in general achieved by using either 5 - 50% TFA in DCM (containing 5% triisopropylsilane) or acetic acid. This resin can also be used in Fmoc peptide synthesis. Carboxylic acids can be released under very mild acidic conditions by treatment with AcOH/TFE/DCM or HFIP in DCM. Completely protected peptides are generated under these conditions. Residues which are sensitive to racemisation during esterification reactions like His and Cys can be attached to the resin without racemisation. Due to the bulkiness of the trityl group, diketopiperazine formation is suppressed which makes this linker ideal for peptides with C-terminal Pro.