That example almost needs an entire book to describe it well. I'll try to keep this short and apologize for its length.
No, there are no adjectives/nouns/clauses/phrases that require the definite article "the." The use of the definite article is necessary when you are trying to convey something specific (aka, "definitive"). No word is inherently definite or partitive. It is how they are used that requires definite or partitive articles.
This issue is made more complicated by the fact that "north" in your example is not an adjective.1 It is a genitive noun2 modifying "main campus." However, let's modify the sentence so the word "north" becomes an adjective. Let's say, "the north end of the main campus." In this case, the genitive noun "end" modifies "main campus" and the adjective "north" modifies "end." (Whoever said English was easy?3)
The reason you might use the definite article "the" in your example is that you are being specific about the location and the bookstore is actually inside the campus. In such a case, it's not "north of the main campus" because that could mean it's located at the North Pole. You're specifically identifying the northern part of the campus itself. Because you are being specific (definite) about the location, you use the definite article "the" ("the north end of the main campus"). On the other hand, if the bookstore really is outside the campus, you would correctly say "the bookstore is north of the main campus" because you need to exclude the campus as a possible location of the bookstore.
Reason #3 is also why you could (and in your case, should) use the definite article with "main campus." Consider these four examples:
(a) "a campus"
Example (a) refers to any campus of any organization. They could be school campuses, business campuses, any campus at all. This partitive condition is very unspecific.
(b) "the campus"
Example (b) is more specific. It restricts the possible campuses to any campus of the one organization related to the statement. (This example is more complex than I've explained, but this will suffice in context of your question.)
(c) "a main campus"
Example (c) is more specific still and limits the campus to the primary campus of any organization, all secondary or branch campuses are excluded.
(d) "the main campus"
Example (d) is the most specific. It identifies the primary campus of the one organization contextually related to the statement.
Thus, "main" is not required to use the definite article. Whether or not the definite article is used depends on the context of what you're trying to say.
- As a final note: you can legitimately say "the bookstore is located at the north end of a main campus." However, there are limited reasons for saying this. Using it as a clue in a treasure hunt is one possibility (participants in the treasure hunt would would need to discover which main campus of several has a bookstore within the northern half of its boundary). It's important to remember, no word is inherently definite or partitive. It's what you are trying to say that makes it definite or partitive.
1 Please note that it would be better in your example to say "the north end of the main campus" or "the north side of the main campus" rather than "the north of the main campus." This is because using "north" as a noun to describe a location is neither definite nor partitive (or it's both...). "North" as a location is one of those cases where you must use the nomnative because you are being specific and unspecific at the same time. The example I used above was "north of the main campus." It describes the specific fact that the bookstore is not in the campus, and the unspecific fact that it's somewhere north of it. You'll see that I use something like "the north end..." frequently after mark for this footnote.
2 A genitive construction, which is being used in your example, is "noun(a) of [a/the/_] noun(b)." Noun(a) modifies noun(b). Articles may or may not exist depending on what you are trying to say. Noun(a) is the genitive noun.
3 There is a possibility that could be used to replace the genitive construction in your example, but I will not explain it in detail in this answer. It is th use of "north" as an adjective in the phrase "north main campus." This is not the genetive form and descibes either a specific main campus where several main campuses exist, or is a descriptor when sections of the main campus are formally identified. Lengthy detail won't be provided because the concept falls outside the context of your question.