2-Methyl-6-phytylquinol and 2,3-dimethyl-5-phytylquinol as precursors of tocopherol synthesis in spinach chloroplasts
b'The incorporation of [Me-14C] from SAM-[Me-14C] into precursors indicates the following sequence of tocopherol synthesis in spinach: 2-methyl-6-phytylquinol (6-phytyltoluquinol) (1a) \\u2192 2,3-dimethyl-5-phytylquinol (phytylplastoquinol) (2a)\\u2192,\\u03b3-tocopherol (5a)\\u2192-tocopherol (6). 1a is particularly preferred to 2-methyl-5-phytylquinol (1b) and 2-methyl-3-phytylquinol (1c). 1a only forms 2a. 2a is converted to 6 via 5a and, to a lesser extent, 2,5-dimethyl-6-phylquinol (2b) to 6 via \\u03b2-tocopherol (5b). Trimethylphytylquinol (3) is not an intermediate in the formation of 6. All reactions are independent of light.'