I want to remove blanks, periods and hyphens from a string and enclose each element of the resulting string by inverted commas. Furthermore, I'd like to ensure that all letters are uppercase. 

I know how to remove a list of special characters but I cannot add enclosing inverted commas due to my lack of experience with regular expressions or other string manipulation functions (e.g., stringr functions).

How can I convert a string such as 

```
test1 <- "A.1, b-1, C"             # start string
test2 <- gsub("[ .-]", "", test1)  # remove period and hyphen

```

to generate the string `'A1','B1','C'`?