In the Book of Daniel, Chapter 3:92 – the term “Son of God” refers to a messenger of God— The angel that entered the fire and saved Shadrach, Meshack, and Abednego from harm.
It is in Chapter 7:13 that the title Son of Man is used. “As the visions during the night continued, I saw One like a son of man coming, on the clouds of heaven; When he reached the Ancient One and was presented before him, He received dominion, glory, and kingship; nations and peoples of every language serve him. His dominion is an everlasting dominion that shall not be taken away, his kingship shall not be destroyed.”
So Jesus using the term Son of Man for Himself, which He did throughout the synoptic gospels, would indicate to the people of His time that He is the Messianic King foretold.
In the Gospel of Matthew, which was written for Jewish converts, we find the high priest confronting Jesus in Mt 26:63-65:
"The high priest then said to him: “I order you to tell us under oath before the living God whether you are the Messiah, the Son of God’ Jesus answered: ‘It is you who say it, But I tell you this: Soon you will see the Son of Man seated at the right hand of the Power and coming on the clouds of heaven.’ At this the high priest tore his robes: ‘He has blasphemed!’”
And again the term “Son of Man” is used in Luke’s account of Stephen’s martyrdom in Acts. Stephen has been arrested in Chapter 7 and stands before the high priest. He gives an account of the history of God’s mercy and salvation to the Jews. In Acts 7:54-58 we read: “Those who listened to his words were stung to the heart; they ground their teeth in anger at him. Stephen meanwhile, filled with the Holy Spirit, looked to the sky above and saw the glory of God, and Jesus standing at God’s right hand. ‘Look!’ he exclaimed, ‘I see an opening in the sky, and the Son of Man standing at God’s right hand.’ The onlookers were shouting aloud, holding their hands over their ears as they did so. Then they rushed at him as one man, dragged him out of the city, and began to stone him…”
It seems to me that everytime Jesus called Himself “Son of Man” He was equating Himself to God, and in the account of Matthew and Acts it would seem that the high priest and other Jewish officials took the term “Son of Man” in this way also.