diff --git a/loki/expression/parser.py b/loki/expression/parser.py
index 3a6a05e80..010887878 100644
--- a/loki/expression/parser.py
+++ b/loki/expression/parser.py
@@ -6,6 +6,7 @@
 # nor does it submit to any jurisdiction.
 
 from sys import intern
+import re
 import pytools.lex
 from pymbolic.parser import Parser as ParserBase
 from pymbolic.mapper import Mapper
@@ -27,7 +28,7 @@ def __init__(self, scope=None):
         super().__init__()
 
     def map_product(self, expr, *args, **kwargs):
-        return sym.Product(expr.children)
+        return sym.Product(tuple(self.rec(child, *args, **kwargs) for child in expr.children))
     map_Mul = map_product
 
     def map_sum(self, expr, *args, **kwargs):
@@ -35,23 +36,25 @@ def map_sum(self, expr, *args, **kwargs):
     map_Add = map_sum
 
     def map_power(self, expr, *args, **kwargs):
-        return sym.Power(base=expr.base, exponent=expr.exponent)
+        return sym.Power(base=self.rec(expr.base),
+                exponent=self.rec(expr.exponent))
 
     def map_quotient(self, expr, *args, **kwargs):
         return sym.Quotient(numerator=expr.numerator, denominator=expr.denominator)
 
     def map_comparison(self, expr, *args, **kwargs):
-        # return sym.Comparison(tuple(self.rec(child, *args, **kwargs) for child in expr.children))
-        return sym.Comparison(left=self.rec(expr.left), operator=expr.operator, right=self.rec(expr.right))
+        return sym.Comparison(left=self.rec(expr.left),
+                operator=expr.operator,
+                right=self.rec(expr.right))
 
     def map_logical_and(self, expr, *args, **kwargs):
-        return sym.LogicalAnd(expr.children)
+        return sym.LogicalAnd(tuple(self.rec(child, *args, **kwargs) for child in expr.children))
 
     def map_logical_or(self, expr, *args, **kwargs):
-        return sym.LogicalOr(expr.children)
+        return sym.LogicalOr(tuple(self.rec(child, *args, **kwargs) for child in expr.children))
 
     def map_logical_not(self, expr, *args, **kwargs):
-        return sym.LogicalNot(expr.children)
+        return sym.LogicalNot(self.rec(expr.child))
 
     def map_constant(self, expr, *args, **kwargs):
         return sym.Literal(expr)
@@ -71,7 +74,7 @@ def map_meta_symbol(self, expr, *args, **kwargs):
     map_array = map_meta_symbol
 
     def map_slice(self, expr, *args, **kwargs):
-        return sym.RangeIndex(expr.children)
+        return sym.RangeIndex(tuple(self.rec(child, *args, **kwargs) for child in expr.children))
 
     map_range = map_slice
     map_range_index = map_slice
@@ -80,6 +83,7 @@ def map_slice(self, expr, *args, **kwargs):
     def map_variable(self, expr, *args, **kwargs):
         return sym.Variable(name=expr.name, scope=self.scope)
 
+    # TODO: incomplete ... better approach possible?
     def map_algebraic_leaf(self, expr, *args, **kwargs):
         if str(expr).isnumeric():
             return self.map_constant(expr)
@@ -108,18 +112,18 @@ class LokiParser(ParserBase):
     _f_notequal = intern('_f_notequal')
     _f_and = intern("and")
     _f_or = intern("or")
-    # _f_not = intern("not")
+    _f_not = intern("not")
 
     lex_table = [
-            (_f_lessequal, pytools.lex.RE(r"\.le\.")),
-            (_f_less, pytools.lex.RE(r"\.lt\.")),
-            (_f_greaterequal, pytools.lex.RE(r"\.ge\.")),
-            (_f_greater, pytools.lex.RE(r"\.gt\.")),
-            (_f_equal, pytools.lex.RE(r"\.eq\.")),
-            (_f_notequal, pytools.lex.RE(r"\.ne\.")),
-            (_f_and, pytools.lex.RE(r"\.and\.")),
-            (_f_and, pytools.lex.RE(r"\.or\.")),
-            # (_f_and, pytools.lex.RE(r"\.not\.")),
+            (_f_lessequal, pytools.lex.RE(r"\.le\.", re.IGNORECASE)),
+            (_f_less, pytools.lex.RE(r"\.lt\.", re.IGNORECASE)),
+            (_f_greaterequal, pytools.lex.RE(r"\.ge\.", re.IGNORECASE)),
+            (_f_greater, pytools.lex.RE(r"\.gt\.", re.IGNORECASE)),
+            (_f_equal, pytools.lex.RE(r"\.eq\.", re.IGNORECASE)),
+            (_f_notequal, pytools.lex.RE(r"\.ne\.", re.IGNORECASE)),
+            (_f_and, pytools.lex.RE(r"\.and\.", re.IGNORECASE)),
+            (_f_or, pytools.lex.RE(r"\.or\.", re.IGNORECASE)),
+            (_f_not, pytools.lex.RE(r"\.not\.", re.IGNORECASE)),
             ] + ParserBase.lex_table
 
     ParserBase._COMP_TABLE.update({
diff --git a/tests/test_expression.py b/tests/test_expression.py
index 4c82850a9..6a60a6f76 100644
--- a/tests/test_expression.py
+++ b/tests/test_expression.py
@@ -1610,6 +1610,14 @@ def test_parser(frontend):
     print(f"{parsed} | {type(parsed)} | children: {parsed.children}")
     parsed = loki_parse('a .or. b')
     print(f"{parsed} | {type(parsed)} | children: {parsed.children}")
+    # parsed = loki_parse('.not. a')
+    parsed = loki_parse('a .or. .not. b')
+    print(f"{parsed} | {type(parsed)}") #  | children: {parsed.child}")
+    print(f"  {fgen(parsed)}")
+    parsed = loki_parse('a .OR. .NOT. b')
+    print(f"{parsed} | {type(parsed)}") #  | children: {parsed.child}")
+    print(f"  {fgen(parsed)}")
 
     parsed = loki_parse('((a + b)/(a - b))**3 + 3.1415', scope=routine)
     print(f"{parsed} | {type(parsed)}")
+    print(f"  {fgen(parsed)}")