Crystalline form ii of melanocortin receptor agonist compound and preparation method therefor

A crystalline form II of a compound of the following formula 1, a pharmaceutically acceptable salt thereof, or a solvate thereof,

• wherein the X-ray powder diffraction pattern has 3 or more characteristic peaks selected from among peaks with the following diffraction angles (2θ values) of:
• 7.77±0.2°, 9.82±0.2°, 10.50±0.2°, 11.37±0.2°, 12.36±0.2°, 15.17±0.2°, 15.46±0.2°, 15.88±0.2°, 16.75±0.2°, 17.59±0.2°, 17.93±0.2°, 18.33±0.2°, 19.64±0.2°, 20.19±0.2°, 21.19±0.2°, 21.71±0.2°, 23.29±0.2°, 23.58±0.2°, 24.42±0.2°, 25.07±0.2°, 25.63±0.2°, 26.31±0.2°, 27.17±0.2°, 27.52±0.2°, and 28.96±0.2°:
• wherein R1 is C2-C5 alkyl.