First Unified Synthesis of Optically Pure Marine Lumazine Alkaloids, ( S )‐6‐(1‐Hydroxypropyl)‐1‐Methyl‐, ‐3‐Methyl‐ and ‐1,3‐Dimethyllumazines

Starting from D‐xylose, ( S )‐6‐(1‐acetoxypropyl)lumazine ( 9 ) was prepared in eleven steps and served as a common chiral intermediate for the preparation of the marine natural products ( S )‐6‐(1‐hydroxypropyl)‐1‐methyllumazine ( 1 ), its 3‐methyl analog ( 2 ), and the 1,3‐dimethyl analog ( 3 ). Regioselective methylation of 9 enabled the first unified synthesis of optically pure N ‐methyllumazine derivatives 1–3 and established the absolute configuration of leucettidine ( 1 ) as ( S )‐6‐(1‐hydroxypropyl)‐1‐methyllumazine.