In 当然，你说的部分也有道理, can we translate 当然 to "of course"?
It seems "truning" is supposed to mean "turning", 转折, turning point, transition, turnaround.  Chinese grammar on the topic of 复句（complex sentences) mentions 偏正复句 (subordinate and main) with 转折关系 as subtopic, (A, 但是 B)


  有些句子，前一个分句往往能引起人们的一种预期，比如说＂他不很喜欢运动＂，这句话往往引起人们的预期-----＂所以身体不能健康＂。如果后一个分句同引起的预期相符合，那么两个分句的意思就是一致的。如果后一个分句同所引起的预期不符合，于是中间就转了一个弯儿，变成＂但是身体很健康＂。这样，两个分句的意思相背，前后不一致，中间有了转折，所以叫做转折关系。
  汉语语法基础


Possible conjunctions: 但是、可是、然而、不过、但、可、却、倒. Complex sentences need not have conjunctions, cf. 紧缩复句 (contracted complex sentence). It would seem translating 当然 as "of course" may not contradict the fact that in some sense there may be a turning point  转折。