Synthesis of (‐)‐β‐homocystine. A contribution to the problem of the high rotatory power of cystine

A new cystine homologue IV showing [α] D −260° has been prepared by applying the Arndt‐Eistert reaction to S‐benzyl‐N‐phthaloyl‐ l ‐cysteine (I). The high [α] D of this compound supports Fredga 's explanation of the high rotatory power of cystine.