Balducci, Daniele et al. published their research in Tetrahedron: Asymmetry in 2005 | CAS: 10297-05-9

Stereocontrolled synthesis of unnatural cyclic dipeptides containing an L-valine unit was written by Balducci, Daniele;Grandi, Alessandro;Porzi, Gianni;Sandri, Sergio. And the article was included in Tetrahedron: Asymmetry in 2005.Safety of 1-Chloro-4-iodobutane This article mentions the following:

Stereoselective synthesis of unusual nonproteinogenic dipeptides I (Y = C:CH₂, R¹ = CO₂Et, R² = H; Y = C:CH₂, R¹ = Me, R² = CO₂Et; Y = CH₂CH₂, R¹ = CO₂Et, R² = H; Y = CH₂CH₂, R¹ = Me, R² = CO₂H; H Y = o-C₆H₄, R¹ = Me, R² = CO₂H), containing an L-valine unit and a cyclic unnatural α-amino acid, has been accomplished starting from the L-valine derived chiral synthon II via alkylation with dihalo derivatives as a key step. The absolute configurations of the new stereocentres were assigned on the basis of ¹H NMR spectra. In the experiment, the researchers used many compounds, for example, 1-Chloro-4-iodobutane (cas: 10297-05-9Safety of 1-Chloro-4-iodobutane).

1-Chloro-4-iodobutane (cas: 10297-05-9) belongs to iodide derivatives. Iodide-containing intermediates are common in organic synthesis, because of the easy formation and cleavage of the C–I bond. The C–I bond is the weakest of the carbon–halogen bonds. These bond strengths correlate with the electronegativity of the halogen, decreasing in the order F > Cl > Br > I. This periodic order also follows the atomic radius of halogens and the length of the carbon-halogen bond.Safety of 1-Chloro-4-iodobutane

Referemce:
Iodide – Wikipedia,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com